As a user I only download needed collections dependencies
As some modules are leaving ansible core to collections, we need to declare collections as dependencies so ansible-galaxy can install them.
pulp_installer provides a set of roles, and the user may not use all the roles, pulp_database role needs community.postgresql for example.
How can we deal with these "conditional dependencies"? "if the user gets pulp_dabase role install community.postgresql else don't install it"