Support RPM package signing service when uploading RPMs via --directory ... --use-temp-repository

[thmo]

Summary

When I upload an RPM via pulp rpm content upload ... --file=foo.rpm it gets signed, but when I upload it via pulp rpm content upload ... --directory=... --use-temp-repository then not.

Steps to reproduce

Put an unsigned RPM in a subdirectory, add it to an existing repo which has a package signing service attached.
Upload it one time using pulp rpm content upload ... --file=dir/foo.rpm, download, verify that it is signed, and then once again upload it using pulp rpm content upload ... --directory=dir --use-temp-repository, download, verify that it isn't.

Expected behavior

In both cases the RPM should be signed.

Pulp and pulp-cli version info

Pulp3 Command Line Interface, Version 0.37.0
Plugin Versions:
  common: 0.37.0

{
  "versions": [
    {
      "component": "core",
      "version": "3.103.3",
      "package": "pulpcore",
      "module": "pulpcore.app",
      "domain_compatible": true
    },
// ...
    {
      "component": "rpm",
      "version": "3.34.0",
      "package": "pulp-rpm",
      "module": "pulp_rpm.app",
      "domain_compatible": true
    },

[thmo]

I guess the package_signing_service and package_signing_fingerprint properties need to be copied/applied to the temp repo.

[thmo]

Probably a duplicate of #1198.

[mdellweg]

I believe this is a duplicate.