add .gpg url (match github behaviour) (#6610)

* add .gpg url (match github behaviour)

* wildcard

* test to export maximum data

* working POC

* add comment for old imported keys

* cleaning

* Update routers/user/profile.go

Co-Authored-By: sapk <sapk@users.noreply.github.com>

* add migration script

* add integration tests

models/models.go

@@ -108,6 +108,7 @@ func init() {
 		new(LFSMetaObject),
 		new(TwoFactor),
 		new(GPGKey),
+		new(GPGKeyImport),
 		new(RepoUnit),
 		new(RepoRedirect),
 		new(ExternalLoginUser),