Disable group access request by default

ZD: https://gitlab.zendesk.com/agent/tickets/36392

I understand in 8.10 there is a checkbox to disable access requests on projects/groups. I agree with Stan, it's probably best to have this disabled by default.

We had a situation where there are 2 ldap groups associated with Master and Owner permissions on a group. The ldap groups have a combined membership of nearly 5000 users.

Someone requested access to the group, and it triggered an email message to all ~5000 users. With addresses in the To: field. There are a couple of issues here:

  1. If group membership is controlled by ldap perhaps it makes more sense to send a message to the ldap group than to each individual member? Of course in our case that would still have been bad, justly slightly less bad.
  1. Probably best to have the recipients in bcc, with a reply-to that prevents a bunch of "please remove me" responses to the group