[MM-37984] Allow Desktop App to authenticate via external providers outside of the app on supported servers (#23795)

* WIP

* Add rate limiting for desktop token API

* Missing mocks

* Style fixes

* Update snapshots

* Maybe use an actual redirect link :P

* Refactoring for tests

* Add tests for server

* Fix lint issue

* Fix tests

* Fix lint

* Add front-end screen component

* Component logic

* Style changes

* Quick style fix

* Lint fixes

* Initial PR feedback

* Enable logging into the browser as well when completing the login process

* Refactor to push more logic to the other component

* Remove unnecessary helper code

* Fix i18n

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/api4/handlers.go

@@ -9,6 +9,8 @@ import (
 	"github.com/mattermost/gziphandler"
 
 	"github.com/mattermost/mattermost/server/public/model"
+	"github.com/mattermost/mattermost/server/public/shared/mlog"
+	"github.com/mattermost/mattermost/server/v8/channels/app"
 	"github.com/mattermost/mattermost/server/v8/channels/web"
 )
 
@@ -200,6 +202,17 @@ func (api *API) APILocal(h handlerFunc) http.Handler {
 	return handler
 }
 
+func (api *API) RateLimitedHandler(apiHandler http.Handler, settings model.RateLimitSettings) http.Handler {
+	settings.SetDefaults()
+
+	rateLimiter, err := app.NewRateLimiter(&settings, []string{})
+	if err != nil {
+		mlog.Error("getRateLimitedHandler", mlog.Err(err))
+		return nil
+	}
+	return rateLimiter.RateLimitHandler(apiHandler)
+}
+
 func requireLicense(c *Context) *model.AppError {
 	if c.App.Channels().License() == nil {
 		err := model.NewAppError("", "api.license_error", nil, "", http.StatusNotImplemented)