An almost identical set of functions to the discord/telegram/matrix
storage ones is now used for accessing invites. No more
parallelism-related issues, yay. Need to do this for everything
eventually.
Get/GetKey/SetKey/DeleteKey methods are used for access to
email/discord/telegram/matrix, everywhere. Mutex added for each, avoids
concurrent read/write issues. Will also make potential transition to
database easier.