Keep a guild's data for a month after BulletBot has left that guild's server

[StrangeRanger]

Is your feature request related to a problem? Please describe. Recently we just found out the hard way that sometimes when discord has an outage, the discord.js guild create and leave event often get called. Due to this, BulletBot will "leave and join" the server, erasing all of the guild's data.

Describe the feature you'd like in detail Instead of immediately erasing a guild's data when BulletBot leaves that guild, wait about a month from when BulletBot left the guild, before deleting all of its data from MongoDB.