various refactors including postgres portability improvements

[chuckadams]

Pull Request

What changed?

• Using epoch-seconds for timestamps instead of datetime, since pgsql and sqlite can't speak any real common dialect.
• Remove N+1 queries for checking status and pulled time. N+1 is fine for sqlite, not for anything else.
• Simplified internals somewhat by merging RevisionMetadataService into ListService (its only consumer)

Why did it change?

To make things work better on postgres.

Did you fix any specific issues?

nein

CERTIFICATION

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