Adds a "User Label" invite field, which is a label applied to users
created with it. This commit contains everything apart from the code to
apply it on account creation.
The captcha library's data struct wasn't being serialized/deserialized
fully, meaning the image was never stored. I never really wanted it to
be stored anyway, but as a compromise, the invite daemon now deletes
captcha images from the DB 20 minutes after generation.
route for generation/enabling of referral for user(s) done? the frontend
is mostly done, but functionality is not there yet. Route for finding
and displaying referral to user is done. Also the config option for
referral is there, in user page settings.
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.