[API] GET / SET User Settings (#16169)

* API: GET/SET User Settings

* linter

* Apply suggestions from code review

* Update modules/structs/user.go

* lint

* fix swagger

* move User2UserSettings to convert

* as per @zeripath "preferences" -> "settings"

Co-authored-by: techknowlogick <matti@mdranta.net>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

routers/api/v1/api.go

@@ -649,6 +649,10 @@ func Routes() *web.Route {
 
 		m.Group("/user", func() {
 			m.Get("", user.GetAuthenticatedUser)
+			m.Group("/settings", func() {
+				m.Get("", user.GetUserSettings)
+				m.Patch("", bind(api.UserSettingsOptions{}), user.UpdateUserSettings)
+			}, reqToken())
 			m.Combo("/emails").Get(user.ListEmails).
 				Post(bind(api.CreateEmailOption{}), user.AddEmail).
 				Delete(bind(api.DeleteEmailOption{}), user.DeleteEmail)