Tangui

This allows turning on niceties like telemetry, redirect or retries, and configuring authentication dynamically for some endpoints.

Metadata should be retrievable through a unique function (for use with `APIacAuthClientJWT` for instance) and the response should be cached, using persistent terms for instance.

https://hexdocs.pm/phoenix/Phoenix.Controller.html#action_fallback/1

https://openid.net/specs/openid-connect-registration-1_0.html#ClientMetadata

https://openid.net/specs/openid-connect-session-1_0.html

For the Mnesia object stores and AtttributeRepository, handle autoclustering. Consider using https://github.com/beardedeagle/mnesiac

When deleting objects from a store during a purge, deletion is done synchronously. To speed up process, this could be parallelized. Depending on the backend: * Mnesia: simply spawning tasks?...

Object stores (Asteroid.Store.*) all share the same code. Refactor it using metaprogramming, with the following options: * backend (Riak, Mnesia, etc.) * indexed fields * object deletion callback to be...