mod_http_oauth2: Implement stateless dynamic client registration Replaces previous explicit registration that required either the additional module mod_adhoc_oauth2_client or manually editing the database. That method was enough to have something to test with, but would not probably not scale easily. Dynamic client registration allows creating clients on the fly, which may be even easier in theory. In order to not allow basically unauthenticated writes to the database, we implement a stateless model here. per_host_key := HMAC(config -> oauth2_registration_key, hostname) client_id := JWT { client metadata } signed with per_host_key client_secret := HMAC(per_host_key, client_id) This should ensure everything we need to know is part of the client_id, allowing redirects etc to be validated, and the client_secret can be validated with only the client_id and the per_host_key. A nonce injected into the client_id JWT should ensure nobody can submit the same client metadata and retrieve the same client_secret

::: {.alert .alert-warning}
This module is an experiment about a more graceful shutdown process.

Graceful shutdown has now been implemented in Prosody trunk and will be
part 0.12. See [issue #1225](https://issues.prosody.im/1225) for
details.
:::

Why
===

When shutting down, a number of sessions, connections and other things
are teared down. Due to all these things happening very quickly,
sometimes e.g. client unavailable notifications don't make it to all
remote contacts because the server-to-server connections are teared down
just after.

How
===

This module works by breaking the shutdown process into separate steps
with a brief pause between them.

It goes something like this

1.  Stop accepting new client connections.
2.  Close all client connections.
3.  Fire event for everything else.
4.  Tell `net.server` to quit the main loop.
5.  ???
6.  Still here? Kill itself.