Create admin API endpoint(s) for sending out emails

[yarikoptic]

We already are sending some emails e.g. when notifying users during registration.

DB has email information for dandiset owners and contacts, and all registered users of the archive.

I think it would make total sense to centralize ability to email DANDI users by use via API, so we could potentially use it in services outside of the dandi-archive, e.g. for admins

• dandi-hub to notify on home directories being reset (Reset home directories after 45 days of inactivity dandi-hub#228) -- so for a specific user
• downtime notifications -- to all registered users
• validation errors reminders -- to corresponding authors of dandisets
• audit summaries -- to corresponding authors of dandisets

there could potentially be use cases even for authenticated users, although not immediately needed

• dandi-cli reportbug {dandiset_id} (does not exist but could)

So having endpoint(s) allowing for those above would have been nice IMHO. It could potentially also take care about proper re-formatting of markdown message text into html and txt versions, adding "branded" header/footnotes and other conveniences.

We could have per dandiset endpoint /dandisets/{dandiset__pk}/contact and then /users/contact with data fields like

• content
• content-encoding (for markdown vs txt vs html)
• subject
• from

Related

• I think it closes Custom announcement emails #569

Current functionality which does emailing

❯ git grep 'def send_'
dandiapi/api/mail.py:def send_ownership_change_emails(dandiset, removed_owners, added_owners):
dandiapi/api/mail.py:def send_registered_notice_email(user: User, socialaccount: SocialAccount):
dandiapi/api/mail.py:def send_new_user_message_email(user: User, socialaccount: SocialAccount):
dandiapi/api/mail.py:def send_approved_user_message(user: User, socialaccount: SocialAccount):
dandiapi/api/mail.py:def send_rejected_user_message(user: User, socialaccount: SocialAccount):
dandiapi/api/mail.py:def send_pending_users_message(users: Iterable[User]):
dandiapi/api/mail.py:def send_dandiset_unembargoed_message(dandiset: Dandiset):
dandiapi/api/mail.py:def send_dandiset_unembargo_failed_message(dandiset: Dandiset):
dandiapi/api/tasks/scheduled.py:def send_pending_users_email() -> None:

so the skeleton is already there in https://github.com/dandi/dandi-archive/blob/HEAD/dandiapi/api/mail.py and there is already the build_message() to serve as a starting point!