Allow reminding from public groups without joining #2512

Summary

Closes #1368 (closed)

If you are not a member of a group currently, you cannot remind, this change changes that.

Steps

Quicktest

1. https://fix-reminds-open-groups-2512.minds.io/groups/profile/1077361820399833094/feed
2. Remind shouldnt even be an option here https://fix-reminds-open-groups-2512.minds.io/groups/profile/1077362222394511374/feed

Fulltest

1. Make a closed group with a non-admin AccountA.
2. Copy the link, log out and in as AccountB join the group and post some things (you may need to accept the user into the group).
3. Ensure that you can interact with the groups posts fine.
4. Leave the group.
5. Try share your posts - you should not be able to.
6. Change to open - check you can remind a post
7. Change to AccountB, check acccount be (having left) can remind.

Regression Scope

Affects reminds within groups, although the change is in the ACL so could cause other issues with reminds in the worst case scenario.