Content view should accept repository label in place of name+product

[kkeane]

SUMMARY

In the content_view module, repositories must be specified as name + product. This can break when the name has been changed in the GUI or elsewhere. One specific example where this happened is with the RHEL 8 repositories; RedHat apparently changed the names of these repositories at some point, removing the architecture name. For instance, the repository with label Red_Hat_Enterprise_Linux_8_for_x86_64_-_BaseOS_RPMs_8 on one of my systems is called:

Red Hat Enterprise Linux 8 for x86_64 - BaseOS RPMs noarch 8

but on another the same repository has the name:

Red Hat Enterprise Linux 8 for x86_64 - BaseOS RPMs 8

This is already possible in the repository_set module; content_view should simply allow the same.

ISSUE TYPE

To resolve this issue, it should be possible to specify the repository by its label (which is immutable) rather than the name + product.

[kkeane]

This appears to be the same issue as requested in #336