Check metricity for message knowledge when logging an out of cache message deletion

[bast0006]

At the current moment when a user deletes a message that the bot has not cached, it outputs a simple message embed including the channel and message ID, which is effectively all the discord API gives us in a message deletion context. However, now that we have Metricity running we are able to cross-check deleted messages with it.

While it's unnecessary to check it for every message, we could use this to get the original author of messages that we aren't provided one, and from that solve the frustrating issue where a user will selfbot-delete their message history and flood the channel with archived messages that aren't attributed to a user anymore.

This may require exposing an endpoint to "get message author" from the Metricity database.