Update notices

Mastodon polls an update server for newer releases and for the end of support of the branch it runs, and records both in software_updates and software_deprecations. Eunha asks the same server the same question about the Mastodon release it implements: eunha builds 4.7.1's schema and serves its API, so when that branch stops receiving fixes, what eunha reproduces is what is going out of support.

Eunha asks nobody anything unless software_update_url names a server, which nothing does by default. Nothing in eunha reads the notices back: they are recorded for a Mastodon that may later boot on the database, and mailed to the instance's own administrators — who on a hosted instance cannot act on them, because only whoever runs the binary can take a release up. Operators who want the end-of-support warning name the server:

software_update_url = "https://api.joinmastodon.org/update-check"

The request then carries the Mastodon version being asked about and eunha's own User-Agent; it does not claim to be Mastodon. A process asks once however many instances it serves — the question is about the release the binary implements, so it is the same for all of them — and records the answer in each of their databases. Instances naming different servers are asked separately, and the set is read afresh each time, so a reload's arrivals and departures are picked up. Whoever tracks releases for a fleet is better served by mise run mastodon:status.