Test - As a user, I can sync modular content

[pulpbot]

Author: kersom (kersom)

Redmine Issue: 5408, https://pulp.plan.io/issues/5408

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As a user, I can sync modulemd content

• support compressed and uncompressed version of modules.yaml
• track a relationship with artifacts
• mark RPMs as modular

As a user, I can sync modulemd_defaults content

• replace with the newer one if checksum changed (can be done in RemoveDuplicates stage)
• do we need to track a relationship to a modulemd? maybe not, can be painful (this part needs additional discussion agreement)

As a user, I can sync modular erratum content