OAuth2 security fixes: redirect URI validation, "Mastodon-Local" security breach fix.

(`POST /api/v1/apps` could create "Mastodon-Local" app wth any redirect_uris,
and if that happened before /web/login is accessed for the first time
then Pleroma used this externally created record with arbitrary
redirect_uris and client_secret known by creator).

lib/pleroma/web/oauth/oauth_controller.ex

@@ -37,6 +37,7 @@ defmodule Pleroma.Web.OAuth.OAuthController do
          true <- Pbkdf2.checkpw(password, user.password_hash),
          {:auth_active, true} <- {:auth_active, User.auth_active?(user)},
          %App{} = app <- Repo.get_by(App, client_id: client_id),
+         true <- redirect_uri in String.split(app.redirect_uris),
          {:ok, auth} <- Authorization.create_authorization(app, user) do
       # Special case: Local MastodonFE.
       redirect_uri =