Support scoped access tokens (#20908)

This PR adds the support for scopes of access tokens, mimicking the
design of GitHub OAuth scopes.

The changes of the core logic are in `models/auth` that `AccessToken`
struct will have a `Scope` field. The normalized (no duplication of
scope), comma-separated scope string will be stored in `access_token`
table in the database.
In `services/auth`, the scope will be stored in context, which will be
used by `reqToken` middleware in API calls. Only OAuth2 tokens will have
granular token scopes, while others like BasicAuth will default to scope
`all`.
A large amount of work happens in `routers/api/v1/api.go` and the
corresponding `tests/integration` tests, that is adding necessary scopes
to each of the API calls as they fit.


- [x] Add `Scope` field to `AccessToken`
- [x] Add access control to all API endpoints
- [x] Update frontend & backend for when creating tokens
- [x] Add a database migration for `scope` column (enable 'all' access
to past tokens)

I'm aiming to complete it before Gitea 1.19 release.

Fixes #4300

services/forms/user_form_test.go

@@ -4,8 +4,10 @@
 package forms
 
 import (
+	"strconv"
 	"testing"
 
+	auth_model "code.gitea.io/gitea/models/auth"
 	"code.gitea.io/gitea/modules/setting"
 
 	"github.com/stretchr/testify/assert"
@@ -83,3 +85,28 @@ func TestRegisterForm_IsDomainAllowed_BlocklistedEmail(t *testing.T) {
 		assert.Equal(t, v.valid, form.IsEmailDomainAllowed())
 	}
 }
+
+func TestNewAccessTokenForm_GetScope(t *testing.T) {
+	tests := []struct {
+		form        NewAccessTokenForm
+		scope       auth_model.AccessTokenScope
+		expectedErr error
+	}{
+		{
+			form:  NewAccessTokenForm{Name: "test", Scope: []string{"repo"}},
+			scope: "repo",
+		},
+		{
+			form:  NewAccessTokenForm{Name: "test", Scope: []string{"repo", "user"}},
+			scope: "repo,user",
+		},
+	}
+
+	for i, test := range tests {
+		t.Run(strconv.Itoa(i), func(t *testing.T) {
+			scope, err := test.form.GetScope()
+			assert.Equal(t, test.expectedErr, err)
+			assert.Equal(t, test.scope, scope)
+		})
+	}
+}