suggest adding channel name to signal contacts in welcome message

context

as a Signalboost channel admin, it can be confusing to keep track of where your channel is! we should suggest that new admins save their channel phone numbers in their contacts to lessen that confusion.

behavior

• WHEN a Signalboost sysadmin creates a new channel
• THEN the admin receives a welcome message that says:

You were just made an admin of the Signalboost channel [beep boop] by the signalboost system administrator. Welcome!

People can subscribe to this channel by sending HELLO to +1555555555 and unsubscribe by sending GOODBYE.

Reply with HELP for more info.

the message should be altered to say:

You were just made an admin of this Signalboost channel, [beep boop] by the Signalboost system administrator. Welcome!

For easy access, add this phone number (+1555555555) to your contacts as [beep boop]. People can subscribe to updates from this channel by sending HELLO to +1555555555 and unsubscribe by sending GOODBYE.

To see a full list of commands, send HELP or check out our how-to guide: https://signalboost.info/how-to.

implementation notes

• every message needs to have a translation for each of our supported languages! (FR/ES/DE)
• unit tests should reflect that!

bonus: there are also some old welcome message strings that should be deleted:

signupRequestReceived: (senderNumber, requestMsg) =>
    `Signup request received from ${senderNumber}:
    ${requestMsg}`,

  signupRequestResponse:
    'Thank you for signing up for Signalboost! You will receive a welcome message on your new channel shortly...',