Update how "joined" message works given LFA registration

[holmesworcester]

Currently, our "joined" message is sent voluntarily by a joining user after they join. It would be better if the "joined" message was triggered by something intrinsic to the user's onboarding process, so that a malicious client could not omit sending the joined message to join silently.

Also, our joined message currently looks like:

"@username has joined and will be registered soon Learn more"

Since we're removing the notion of username registration, it should simply say:

@username has joined

or better, if it's easy:

@username has joined Community-name

[Hamza20203064]

Hi @holmesworcester , This issue can be fixed by removing the username registration notification. If you assign it to me under PLDG Cohort-2, I would like to work on it.

[holmesworcester]

Thanks for offering to help! We'd prefer to keep the notification, and change the trigger and the notification text.

Also, @Hamza20203064 if you'd like to join our Slack and pick some issues that best fit your goals, drop me a line and I'll send you an invite: h@quiet.chat