System Flows e.g. for Invite eMails

Summary Instead of hard coded business logic in directus source, parts could be transferred to the powerful flows system, allowing users to adapt the logic to their needs. A set of "system flows" would ship with directus - like directus_ system collections to have an out of the box working configuration. But if needed, the flows / business logic can be modified to match project specific needs (see design details). Basic Example One first use cases in mind are the user invite and password reset mails. As stated in #8239, #7372, #16673, #15590, #17485, #3115, and probably more, users have the need for customizing system mails e.g. subject or an i18n body. A brief example on how this could work for user invite mails: • Scope of flow Trigger Event Hook would be extend with users.invite, which provides as payload data which was before handed into the template (JWT, and email). Maybe also the role the user gets assigned, or key of the bare user record in the db..…