Change record status: 
Project: 
Introduced in branch: 
2.0.x
Introduced in version: 
2.0.0
Description: 

$group_content_foo -> $group_relationship_foo
GroupContentBar -> GroupRelationshipBar
BazGroupContent -> BazGroupRelationship

Machine names remain unaffected unless otherwise specified in a separate, dedicated change record.

Impacts: 
Module developers
Site templates, recipes and distribution developers