feature-request(dnf): Set priorities for added repos (files,copr,nonfree)

[lukasgierth]

Right now i am having the following problem: I add a copr of mine which has a package with the same name as a package from the main fedora repo.

Problem: When i set to explicitely install from my repo i get an error, because a dependency is only available in the main repo that is now disabled for this install.

Having the option to set the priorities for the repos would solve this problem.

[bbonsign]

@lukasgierth I ran into the same issue recently and came accross this section of the dnf module docs, which solved the problem for me: https://github.com/blue-build/modules/tree/main/modules/dnf#packages-from-specific-repositories