Adds RemoteId to the fields to clean when coming from the API (#27047)

* Cleans the RemoteId when creating a user through the API

* Replace bad usage of the API with an App call in tests

---------

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

server/public/model/user.go

@@ -657,6 +657,7 @@ func (u *User) SanitizeInput(isAdmin bool) {
 		u.AuthService = ""
 		u.EmailVerified = false
 	}
+	u.RemoteId = NewString("")
 	u.DeleteAt = 0
 	u.LastPasswordUpdate = 0
 	u.LastPictureUpdate = 0