Support S3-compatible Pulp storage

[jakduch]

Summary

Add optional S3-compatible content storage while keeping filesystem storage as the default.

This continues #379 against current master and addresses its open review findings:

• install the stable pulpcore-storage-s3 capability from theforeman/pulpcore-packaging#3189, which follows the django-storages packaging in #3186;
• preserve Django’s local staticfiles backend so collectstatic continues to work;
• omit MEDIA_ROOT for object storage so Django's default empty value applies;
• avoid managing the unused local media directory.

storage_options is passed through to django-storages, which supports AWS S3 and S3-compatible endpoints without hard-coding provider-specific options.

Verification

• bundle exec rake spec: 308 examples, 0 failures
• acceptance coverage applies the S3 configuration twice, verifies the installed capability and generated settings, and runs pulpcore-manager check on the nightly repository where the new package is introduced
• Puppet lint and syntax checks pass
• git diff --check passes

This is the installer-side prerequisite for optional object storage in the experimental theforeman/foreman-kubernetes integration.

AI assistance disclosure: OpenAI Codex (GPT-5.6 Sol High).

[ekohl]

This reads well. Perhaps you could also add an acceptance test that exercises the new code paths? Or would that be too hard?

[jakduch]

Added in c882d2a. The acceptance test applies the S3 configuration twice, verifies the package and generated settings, and runs pulpcore-manager check.

It is limited to the nightly repository because pulpcore-storage-s3 is introduced by theforeman/pulpcore-packaging#3189 and is not available in the older stable repositories.

[alexjfisher]

I can take a look tomorrow too. I'm using S3, and was doing some bits in my profile code around it, that I was planning to turn into some upstream module patch at some stage.

[alexjfisher]

LGTM. I can't see anything I currently have fudged into my profile that couldn't be replaced when this goes into the module.