Add support for login event?

[jas8522]

• sign_up event: https://developers.google.com/analytics/devguides/collection/ga4/reference/events?client_type=gtag#sign_up
• login event: https://developers.google.com/analytics/devguides/collection/ga4/reference/events?client_type=gtag#login

Would need to be triggered under these hooks:

• sign_up: ClientAreaRegister - https://developers.whmcs.com/hooks-reference/client-area-interface/#clientarearegister
• login: UserLogin - https://developers.whmcs.com/hooks-reference/authentication/#userlogin

[jas8522]

sign_up event added in 5578eeea704bd01ae40014121a22ae4971abe307