Description of problem:
After configuring a custom repository as explained in the upstream documentation [0], it looks like the metadata related to this repository does not expire.
Adding a package to this repository (and updating the repodata) is never seen by the composer.

Adding "metadata_expire = 300" (`man dnf.conf`) in the toml file used to add a repository through composer-cli did not help to have this package "depsolvable".

[0] https://www.osbuild.org/guides/user-guide/managing-repositories.html#custom-3rd-party-repositories

Version-Release number of selected component (if applicable):
osbuild-composer-33.2-1.el8.x86_64
osbuild-35-3.el8.noarch

How reproducible:
Always

Steps to Reproduce:
1. Create a repository named 'repotest' shared via http with pkg1.rpm and pkg2.rpm

2. Create a toml file to define this repo
id = "repotest"
name = "repotest"
type = "yum-baseurl"
url = "http://192.168.122.1/repotest"
check_gpg = false
check_ssl = false
system = false

3. Add this repo

1. composer-cli sources add repotest.toml

4. Run a depsolve with a blueprint containing pkg

1. composer-cli blueprints depsolve myimage
   2021-11-24 12:07:21,589: myimage: DNF error occured: MarkingErrors: Error occurred when marking packages for installation: Problems in request:
   missing packages: pkg3

5. Add the missing pkg3.rpm to the custom repository (update it with createrepo -u...)

6. Run a new depsolve and observe the issue - which was expected in a first time - still occurs.

Expected results:
The ability to use metadata_expire from the composer sources, and possibly a composer command to clear the cache.

Additional info:
Removing the cache in /var/cache/osbuild-composer/* and restarting the daemon fixed the issue.