Grouper does not currently have a way of supporting autoincremented IDs as used by Cake. UUIDs could be used instead, but make COmanage URLs much uglier to manage. (There's also a minor performance hit, but not worth worrying about currently.)

For now, the CoGroup and CoGroupMember models can reconfigure their validation rules to expect char instead, however the better long term approach is to use an autoincremented ID created by Grouper.

(eg: If petitions can create groups/group membership, then petitions will have foreign keys into CoGroup and CoGroupMember, and having to track different types of foreign keys (ie: integer for CoPerson but char for CoGroup) doesn't seem right.