Version based RPM retention policy per repository

[praiskup]

Consider we have 3 packages in the repository (referenced by the latest repo version):

1. foo-1.1-1.x86_64.rpm - built 2022-01-01
2. foo-1.0-1.x86_64.rpm - built 2022-02-01
3. foo-1.0-2.x86_64.rpm - built 2022-03-01

When a user installs foo using DNF, 1. is installed because it has the
highest NVR (even though it effectively comes from an older build).
Providing 2. and 3. is often a waste of storage space (at least in the
Copr case where we don't have the storage capacity for all the builds).

We need to have an automation that would (by opt-in) automatically remove
these obsoleted packages after some predefined time (e.g. 14 days by
default, that is package 2 not sooner than 2022-02-15 and 3 not sooner
than 2022-03-15).

This workflow is what Copr currently has implemented via prunerepo project.

Describe the solution you'd like

Something like "rpm repository modify --retain-old-package-versions 14"
(defaults to infinite).

Additional context

This issue is a part of the future Copr <-> PULP integration efforts.

[praiskup]

Sorry for the duplicate, moving to #2946

[praiskup]

I meant duplicate to: #2909