feat: support federation properly

[90-008]

(this only applies to refactored branch currently)

loqui does not support federation properly. Things to take care of:

• create ID types for guilds / private channels that include server_id so we can distinguish them properly in our state,
• create a connection struct for managing server connections, implement a call method on it that takes a server_id and request,
• make sure all server_ids we have in codebase is used.