Send e-mail on first username set

packages/rocketchat-lib/server/functions/setUsername.coffee

@@ -16,6 +16,10 @@ RocketChat.setUsername = (user, username) ->
 
 	previousUsername = user.username
 
+	# If first time setting username, send Enrollment Email
+	if not previousUsername and RocketChat.settings.get 'Accounts_Enrollment_Email'
+		Accounts.sendEnrollmentEmail(user._id)
+
 	# Username is available; if coming from old username, update all references
 	if previousUsername
 		RocketChat.models.Messages.updateAllUsernamesByUserId user._id, username