Feat/msc4258 fed user dir

[mcalinghee]

MSC Federated User Directory :
https://github.com/tchapgouv/matrix-spec-proposals/blob/fed-user-dir/proposals/4258-federated-user-directory.md

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
  • Use markdown where necessary, mostly for code blocks.
  • End with either a period (.) or an exclamation mark (!).
  • Start with a capital letter.
  • Feel free to credit yourself, by adding a sentence "Contributed by @github_username." or "Contributed by [Your Name]." to the end of the entry.
• Code style is correct
  (run the linters)

TODO:

• add configuration to allow federated user search (msc4258_enabled)
• add search token
• perfom test on performance side
• add search scope
• make sure CI are passing through
• rework selection of target homeserver
• more results on more servers(when too many servers) if user asks for it

[mcalinghee]

il faudra changer cette cle de cache (pour y mettre le search token?) et peut etre changer le timeout de 1h(timeout_ms=60 * 60 * 1000)

[mcalinghee]

voir si on met ceci a 10