checkUserCredentials( $username, $password) : TRUE
Grant access tokens for basic user credentials.
Check the supplied username and password for validity.
You can also use the $client_id param to do any checks required based on a client, if you need that.
Required for OAuth2::GRANT_TYPE_USER_CREDENTIALS.
Username to be check with.
Password to be check with.
if the username and password are valid, and FALSE if it isn't. Moreover, if the username and password are valid, and you want to