OAuth: Support /revoke endpoint for revoking tokens

(for compatibility with Mastodon)

lib/pleroma/web/oauth/oauth_controller.ex

@@ -118,6 +118,18 @@ def token_exchange(
     token_exchange(conn, params)
   end
 
+  def token_revoke(conn, %{"token" => token} = params) do
+    with %App{} = app <- get_app_from_request(conn, params),
+         %Token{} = token <- Repo.get_by(Token, token: token, app_id: app.id),
+         {:ok, %Token{}} <- Repo.delete(token) do
+      json(conn, %{})
+    else
+      _error ->
+        # RFC 7009: invalid tokens [in the request] do not cause an error response
+        json(conn, %{})
+    end
+  end
+
   defp fix_padding(token) do
     token
     |> Base.url_decode64!(padding: false)

lib/pleroma/web/router.ex

@@ -93,6 +93,7 @@ def user_fetcher(username_or_email) do
     get("/authorize", OAuthController, :authorize)
     post("/authorize", OAuthController, :create_authorization)
     post("/token", OAuthController, :token_exchange)
+    post("/revoke", OAuthController, :token_revoke)
   end
 
   scope "/api/v1", Pleroma.Web.MastodonAPI do