Allow passing in member for calculating effective permissions

[schnapster]

Description:

Allow passing in a proper Member object into GuildChannel#getEffectivePermissions instead of just a SnowflakeId.

Justification:

This allows optimizations of rest requests in certain situations.
When the GUILDS intent is used, but not the GUILD_MEMBERS intent, calling getEffectivePermissions with just the SnowflakeId of the user will result in a REST request to fetch the member (but no other request, as the owner, role data, etc can be served from the entity cache). In some situations it is unnecessary to fetch the member from the API. A MessageCreateEvent contains a Member object for the author, so if we wanted to check their permissions, we could avoid that API request by passing that member object to getEffectivePermissions, reducing the amount of necessary API requests to 0.

Another smaller use case would be checking self permissions. At a large scale, with the GUILD_MEMBERS intent not enabled, a bot author might want to have the option to handle caching their self member objects outside the entity cache, to heuristically reduce API calls for certain non-critical self permissions checks.

[darichey]

That makes sense. Ironically, I think throughout the public API, we opted to accept Snowflakes instead of entities exactly because we didn't want people to fetch an entity unnecessarily. In this case, that's misleading (and detrimental) because we fetch it internally anyways.

I would be in favor of deprecating the Snowflake overload for this method. We should also look for other methods that do something similar (I'm really not sure how to perform that search though).