Add Memory of Rejection and Removal to Goup

The intention of this is to prevent spamming when inviting, adding, and removing users from groups. These actions can results in E-mails being sent to users.

If a group member with permissions to invite and remove members ever removes a member from a group (this functionality is not available yet) the User _id and email address should be captured and stored in a property on the Group.

Likewise, if a user removes themselves or rejects an invitation those group members should not be able to continue to span the invitee with E-mails to join. The email address should be captured and stored in a property on the Group.

We would need to make a new property, or multiple properties, for this. These properties would be private and would not be exposed to clients via endpoints, it is for internal purposes only.

Using this information, we can add checks in the invite - accept - intentionally reject invitation - intentionally leave project workflows.

Start by tracing the invite, accept, intentionally reject invitation, intentionally leave project, and member removal workflows. Determine how group membership and email notifications are represented, then define the private Group data and checks needed to prevent repeat invitations; done means those workflows retain rejection or removal information without exposing it through endpoints.

Written by the indexing model from the issue text.