admin: channels joined by invitation are not saved to config

[dgw]

sopel/sopel/builtins/admin.py

Lines 290 to 302 in 7693af3

	@plugin.event('INVITE')
	@plugin.priority('low')
	def invite_join(bot, trigger):
	"""Join a channel Sopel is invited to, if the inviter is an admin."""
	channel = trigger.args[1]
	if trigger.admin:
	LOGGER.info(
	'Got invited to "%s" by an admin.', channel)
	bot.join(channel)
	elif bot.config.admin.auto_accept_invite:
	LOGGER.info(
	'Got invited to "%s"; admin.auto_accept_invite is on', channel)
	bot.join(channel)

The docstring is a bit incorrect, too, given auto_accept_invite.

Not saving channel membership resulting from invitations appears to trace all the way back to #1492 for 7.0.

(Yes, I'm intentionally leaving this out of 8.0.)