Allow a user to enable "debug" information on notifications

[ryanlerch]

When a user is getting a lot of notifications from a lot of a lot of rules, it may be useful to have extra information attached to each notification delivered. i'm thinking

• the fedora-messaging message ID (or a link to the message in datagrepper)
• the FMN rule that sent the message

It probably makes the most sense to add this to the generation rules right? Or make it a global user setting?