Restructure documentation. Now the documentation has installation, administration, usage, development, contributing the 5 main parts (#23629)

- **Installation**: includes how to install Gitea and related other
tools, also includes upgrade Gitea
- **Administration**: includes how to configure Gitea, customize Gitea
and manage Gitea instance out of Gitea admin UI
- **Usage**: includes how to use Gitea's functionalities. A sub
documentation is about packages, in future we could also include CI/CD
and others.
- **Development**: includes how to integrate with Gitea's API, how to
develop new features within Gitea
- **Contributing**: includes how to contribute code to Gitea
repositories.

After this is merged, I think we can have a sub-documentation of `Usage`
part named `Actions` to describe how to use Gitea actions

---------

Co-authored-by: John Olheiser <john.olheiser@gmail.com>

docs/content/doc/help/faq.en-us.md

@@ -43,7 +43,7 @@ On the other hand, 1.x.x downloads should never change.
 
 To migrate from Gogs to Gitea:
 
-- [Gogs version 0.9.146 or less]({{< relref "doc/upgrade/from-gogs.en-us.md" >}})
+- [Gogs version 0.9.146 or less]({{< relref "doc/installation/upgrade-from-gogs.en-us.md" >}})
 - [Gogs version 0.11.46.0418](https://github.com/go-gitea/gitea/issues/4286)
 
 To migrate from GitHub to Gitea, you can use Gitea's built-in migration form.
@@ -90,7 +90,7 @@ https://github.com/loganinak/MigrateGitlabToGogs
 
 There are a few places that could make this show incorrectly.
 
-1. If using a reverse proxy, make sure you have followed the correction directions in the [reverse proxy guide]({{< relref "doc/usage/reverse-proxies.en-us.md" >}})
+1. If using a reverse proxy, make sure you have followed the correction directions in the [reverse proxy guide]({{< relref "doc/administration/reverse-proxies.en-us.md" >}})
 2. Make sure you have correctly set `ROOT_URL` in the `server` section of your `app.ini`
 
 If certain clone options aren't showing up (HTTP/S or SSH), the following options can be checked in your `app.ini`
@@ -103,7 +103,7 @@ If certain clone options aren't showing up (HTTP/S or SSH), the following option
 
 This error occurs when the reverse proxy limits the file upload size.
 
-See the [reverse proxy guide]({{< relref "doc/usage/reverse-proxies.en-us.md" >}}) for a solution with nginx.
+See the [reverse proxy guide]({{< relref "doc/administration/reverse-proxies.en-us.md" >}}) for a solution with nginx.
 
 ## Custom Templates not loading or working incorrectly
 
@@ -116,7 +116,7 @@ The correct path for the template(s) will be relative to the `CustomPath`
     If that doesn't exist, you can try `echo $GITEA_CUSTOM`
 
 2. If you are still unable to find a path, the default can be [calculated above](#where-does-gitea-store-what-file)
-3. Once you have figured out the correct custom path, you can refer to the [customizing Gitea]({{< relref "doc/advanced/customizing-gitea.en-us.md" >}}) page to add your template to the correct location.
+3. Once you have figured out the correct custom path, you can refer to the [customizing Gitea]({{< relref "doc/administration/customizing-gitea.en-us.md" >}}) page to add your template to the correct location.
 
 ## Active user vs login prohibited user
 
@@ -126,7 +126,7 @@ A "login prohibited" user is a user that is not allowed to log in to Gitea anymo
 
 ## Setting up logging
 
-- [Official Docs]({{< relref "doc/advanced/logging-documentation.en-us.md" >}})
+- [Official Docs]({{< relref "doc/administration/logging-documentation.en-us.md" >}})
 
 ## What is Swagger?
 
@@ -134,7 +134,7 @@ A "login prohibited" user is a user that is not allowed to log in to Gitea anymo
 
 All Gitea instances have the built-in API and there is no way to disable it completely.
 You can, however, disable showing its documentation by setting `ENABLE_SWAGGER` to `false` in the `api` section of your `app.ini`.
-For more information, refer to Gitea's [API docs]({{< relref "doc/developers/api-usage.en-us.md" >}}).
+For more information, refer to Gitea's [API docs]({{< relref "doc/development/api-usage.en-us.md" >}}).
 
 You can see the latest API (for example) on <https://try.gitea.io/api/swagger>.
 
@@ -149,7 +149,7 @@ There are multiple things you can combine to prevent spammers.
 1. By whitelisting or blocklisting certain email domains
 2. By only whitelisting certain domains with OpenID (see below)
 3. Setting `ENABLE_CAPTCHA` to `true` in your `app.ini` and properly configuring `RECAPTCHA_SECRET` and `RECAPTCHA_SITEKEY`
-4. Settings `DISABLE_REGISTRATION` to `true` and creating new users via the [CLI]({{< relref "doc/usage/command-line.en-us.md" >}}), [API]({{< relref "doc/developers/api-usage.en-us.md" >}}), or Gitea's Admin UI
+4. Settings `DISABLE_REGISTRATION` to `true` and creating new users via the [CLI]({{< relref "doc/administration/command-line.en-us.md" >}}), [API]({{< relref "doc/development/api-usage.en-us.md" >}}), or Gitea's Admin UI
 
 ### Only allow/block certain email domains
 
@@ -175,7 +175,7 @@ At some point, a customer or third party needs access to a specific repo and onl
 
 ### Enable Fail2ban
 
-Use [Fail2Ban]({{< relref "doc/usage/fail2ban-setup.en-us.md" >}}) to monitor and stop automated login attempts or other malicious behavior based on log patterns
+Use [Fail2Ban]({{< relref "doc/administration/fail2ban-setup.en-us.md" >}}) to monitor and stop automated login attempts or other malicious behavior based on log patterns
 
 ## How to add/use custom themes
 
@@ -328,24 +328,24 @@ You may want to set this value to `60m` or `120m`.
 
 ## How can I create users before starting Gitea
 
-Gitea provides a sub-command `gitea migrate` to initialize the database, after which you can use the [admin CLI commands]({{< relref "doc/usage/command-line.en-us.md#admin" >}}) to add users like normal.
+Gitea provides a sub-command `gitea migrate` to initialize the database, after which you can use the [admin CLI commands]({{< relref "doc/administration/command-line.en-us.md#admin" >}}) to add users like normal.
 
 ## How can I enable password reset
 
-There is no setting for password resets. It is enabled when a [mail service]({{< relref "doc/usage/email-setup.en-us.md" >}}) is configured, and disabled otherwise.
+There is no setting for password resets. It is enabled when a [mail service]({{< relref "doc/administration/email-setup.en-us.md" >}}) is configured, and disabled otherwise.
 
 ## How can a user's password be changed
 
 - As an **admin**, you can change any user's password (and optionally force them to change it on next login)...
   - By navigating to your `Site Administration -> User Accounts` page and editing a user.
-  - By using the [admin CLI commands]({{< relref "doc/usage/command-line.en-us.md#admin" >}}).
+  - By using the [admin CLI commands]({{< relref "doc/administration/command-line.en-us.md#admin" >}}).
 
-    Keep in mind most commands will also need a [global flag]({{< relref "doc/usage/command-line.en-us.md#global-options" >}}) to point the CLI at the correct configuration.
+    Keep in mind most commands will also need a [global flag]({{< relref "doc/administration/command-line.en-us.md#global-options" >}}) to point the CLI at the correct configuration.
 - As a **user** you can change it...
   - In your account `Settings -> Account` page (this method **requires** you to know your current password).
   - By using the `Forgot Password` link.
 
-    If the `Forgot Password/Account Recovery` page is disabled, please contact your administrator to configure a [mail service]({{< relref "doc/usage/email-setup.en-us.md" >}}).
+    If the `Forgot Password/Account Recovery` page is disabled, please contact your administrator to configure a [mail service]({{< relref "doc/administration/email-setup.en-us.md" >}}).
 
 ## Why is my markdown broken
 
@@ -457,6 +457,6 @@ If you are using Cloudflare, turn off the auto-minify option in the dashboard.
   - You can also check `<ROOT_URL>/admin/config` for the repository root path.
 - Ensure that the user/org exists that you want to adopt repositories for.
 - As an admin, go to `<ROOT_URL>/admin/repos/unadopted` and search.
-  - Users can also be given similar permissions via config [`ALLOW_ADOPTION_OF_UNADOPTED_REPOSITORIES`]({{< relref "doc/advanced/config-cheat-sheet.en-us.md#repository" >}}).
+  - Users can also be given similar permissions via config [`ALLOW_ADOPTION_OF_UNADOPTED_REPOSITORIES`]({{< relref "doc/administration/config-cheat-sheet.en-us.md#repository" >}}).
 - If the above steps are done correctly, you should be able to select repositories to adopt.
-  - If no repositories are found, enable [debug logging]({{< relref "doc/advanced/config-cheat-sheet.en-us.md#repository" >}}) to check for any specific errors.
+  - If no repositories are found, enable [debug logging]({{< relref "doc/administration/config-cheat-sheet.en-us.md#repository" >}}) to check for any specific errors.