Add a way for bots to know which guild an emoji is from

[abitofevrything]

Currently, there is no way for a bot to reliably identify the guild an emoji came from. The best way to do so currently is to list the emojis for every guild the client is in, cache the results, and then perform a lookup by ID when an event involving an emoji is received (e.g Message Reaction Add).

It seems strange for something to be possible via a "hack" but have no official API support. Therefore, I suggest adding a nullable snowflakeguild_id field to the Emoji object, which is null when the emoji is a standard emoji and the ID of the guild that created the emoji otherwise. An emoji that is deleted from a guild should still have its guild_id field point to the guild.

It's worth noting that the Discord client does have a way to obtain this information - the endpoint /emojis/<id>/guild returns a partial Guild object for the guild the emoji was created in (or 404 if the guild is private). This endpoint is undocumented, and cannot be used by bots, so it is not a solution (currently) to this problem. Adding access to this endpoint for bots would be nice, but adding the guild_id field would be even nicer.

For some context as to why we want to know this information, we are currently rewriting our wrapper around the Discord API for Dart. For every other "main" type of entity, we were able to gather enough information to add support for the fetch, update and delete operations on those entities from only the information contained in the Gateway event. For emojis, we only have the emoji ID, but the endpoints for fetching/updating/deleting require the Guild id to be known (/guilds/<id>/emojis/<id>), so we can't add support for those operations.