Write and run management command to send email notifying registered API users of the new api.openverse.org domain

[sarayourfriend]

Description

Part of https://docs.openverse.org/projects/proposals/infrastructure_improvements/20240105_implementation_plan_move_remaining_services_to_openverse_org.html#move-the-django-api-to-api-openverse-org

Refer to this previous email-sending management command for an example of how we have managed this in the past. Record successfully sent email recipients in Redis, to ensure the command is idempotent.

Staff only because this will require composing the email body and then running the management command in production

Blocked by https://github.com/WordPress/openverse-infrastructure/issues/778

The email body should specify a date for when the openverse.engineering domains will start permanently redirecting to openverse.org domain. That date should be at least two weeks in the future from the date the email is sent.

Update https://github.com/WordPress/openverse-infrastructure/issues/783 with the decided date.

Ideally #3743 is completed around the same time and includes the decided transition date.

[sarayourfriend]

The emails are sent as of 2024-05-08T00:59:58.366Z.