AgsDataConnectionManager and AgsConnection are removed in 2.0.x. The object was somehow overhelming because you can have properties.

The AgsConnectable interface provides 2 new functions: void ags_connectable_connect_connection(AgsConnectable*, GObject*) and void ags_connectable_disconnect_connection(AgsConnectable*, GObject*).

Dependencies not know an instantiation time can be later connected.