Add test notification tool (#28334)

* Add test notification tool

* Add frontend styles

* Remove option from admin view

* Refactor create post and add translations

* Fix several CI errors

* Fix API and frontend snapshots

* Refactor trailing and leading icon on buttons

* Add different button states

* i18n-extract

* Fix wrong text

* Add tests

* Fix wrong string

* Fix test

* feat: E2E send test notifications (#28371)

* Refactor send desktop notification

* Address rest of the feedback

* Fix tests

* Add correct link

* Fix test

---------

Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: yasserfaraazkhan <attitude3cena.yf@gmail.com>

server/public/model/client4.go

@@ -344,6 +344,10 @@ func (c *Client4) testEmailRoute() string {
 	return "/email/test"
 }
 
+func (c *Client4) testNotificationRoute() string {
+	return "/notifications/test"
+}
+
 func (c *Client4) usageRoute() string {
 	return "/usage"
 }
@@ -4820,6 +4824,15 @@ func (c *Client4) TestEmail(ctx context.Context, config *Config) (*Response, err
 	return BuildResponse(r), nil
 }
 
+func (c *Client4) TestNotifications(ctx context.Context) (*Response, error) {
+	r, err := c.DoAPIPost(ctx, c.testNotificationRoute(), "")
+	if err != nil {
+		return BuildResponse(r), err
+	}
+	defer closeBody(r)
+	return BuildResponse(r), nil
+}
+
 // TestSiteURL will test the validity of a site URL.
 func (c *Client4) TestSiteURL(ctx context.Context, siteURL string) (*Response, error) {
 	requestBody := make(map[string]string)