Update reminder jobs to save username separate from message #138
Description
Currently, when a user calls \remind team [...] or remind me [...], the relevant at-mentions are constructed and saved as part of the reminder's message.
The becomes a problem if the user chooses to update their message: the at-mention is not automatically preserved; the new message input will overwrite it.
We should save the username as a separate field on the job, and reconstruct the at-mention when a message is formatted for display and/or triggered.