Add support for ssh commit signing (#17743)

* Add support for ssh commit signing

* Split out ssh verification to separate file

* Show ssh key fingerprint on commit page

* Update sshsig lib

* Make sure we verify against correct namespace

* Add ssh public key verification via ssh signatures

When adding a public ssh key also validate that this user actually
owns the key by signing a token with the private key.

* Remove some gpg references and make verify key optional

* Fix spaces indentation

* Update options/locale/locale_en-US.ini

Co-authored-by: Gusted <williamzijl7@hotmail.com>

* Update templates/user/settings/keys_ssh.tmpl

Co-authored-by: Gusted <williamzijl7@hotmail.com>

* Update options/locale/locale_en-US.ini

Co-authored-by: Gusted <williamzijl7@hotmail.com>

* Update options/locale/locale_en-US.ini

Co-authored-by: Gusted <williamzijl7@hotmail.com>

* Update models/ssh_key_commit_verification.go

Co-authored-by: Gusted <williamzijl7@hotmail.com>

* Reword ssh/gpg_key_success message

* Change Badsignature to NoKeyFound

* Add sign/verify tests

* Fix upstream api changes to user_model User

* Match exact on SSH signature

* Fix code review remarks

Co-authored-by: Gusted <williamzijl7@hotmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

vendor/golang.org/x/crypto/ssh/cipher.go

@@ -18,7 +18,7 @@ import (
 	"io/ioutil"
 
 	"golang.org/x/crypto/chacha20"
-	"golang.org/x/crypto/poly1305"
+	"golang.org/x/crypto/internal/poly1305"
 )
 
 const (