CiviCRM Profile - Support for Tags and Groups

Allow users to add 'Tags' and 'Groups' as meta-elements in a given Profile.

For Groups, we also need to add a new column (visible) to civicrm_group to control the visibility of the group (same enum values as uf_group.visible). Groups with visibility = User and User Admin are NOT included when group selector is exposed via Profile.

NOTE: We may want to consider other related Group properties as described in the DGroups 'spec' - altho they imply functionality above and beyond what we have on our roadmap at this point....

DGroups group properites
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• Subscription requests settings. A group can be:
  • Open (anyone can join)
  • Moderated (join requests are approved by the group administrator)
  • Invite-only (only the administrator can initiate join requests)

• If you wish this group to be available for users to choose from when they register,
  check registration form

• If you'd like this group to be listed in the public groups directory, check list in
  groups directory.