Document admin/email API endpoint so I can automnate end user emails
Description
(Include problem, use cases, benefits, and/or goals)
Use case: As an admin, during an upgrade of GitLab EE after smoke tests have passed, I would like to automatically send an email to all end users.
Proposal
Document the admin/email endpoint so that users know what authenticity_token is.
Links / references
Documentation blurb
(Write the start of the documentation of this feature here, include:
- Why should someone use it; what's the underlying problem.
- What is the solution.
- How does someone use this
During implementation, this can then be copied and used as a starter for the documentation.)