Ticket 669 - Implement sync for Discord threads without tickets

[philion]

Implements changes related to creating redmine ticket from Discord.

The command, '/scn sync', when executed within an existing Discord thread, creates a new ticket from the existing thread, such that:

• The new ticket has the subject taken from the existing thread title
• The new ticket will have a description the matches the title, with a description of how it was created
• The ticket's creator is the redmine user associated with the Discord account
• The new ticket tracker will be based on the parent channel of the thread
• Each message in the thread will be copied as a note to the new ticket, with the discord user translated to redmine user

Further, new tickets created with '/new' will automatically create threads.