Image digests for referencing bundles

[anik120]

Description of the change:

• Change schema of OperatorBundle to include field 'bundlepath'
• Extend GetBundle API to return bundle image path
• Modify GetBundle API to return struct with avaiable fields
  instead of error while querrying empty bundles

Reviewer Checklist

• Implementation matches the proposed design, or proposal is updated to match implementation
• Sufficient unit test coverage
• Sufficient end-to-end test coverage
• Docs updated or added to /docs
• Commit messages sensible and descriptive

[anik120]

@ecordell @kevinrizza I've rebased it on top of #101. PTAL

[ecordell]

Overall this looks great - can you add positive tests for the grpc apis (i.e. if bundle = nil and bundlepath = path in the db, the grpc apis return the right thing)?

[ecordell]

I think you can delete this

[anik120]

can you add positive tests for the grpc apis (i.e. if bundle = nil and bundlepath = path in the db, the grpc apis return the right thing)?

@ecordell looks like there's two ways we can add this test with the way the tests are laid out now:

1. Wait for Adding OPM cli with registry add and rm commands #89 to merge which will then allow us to add an operator bundle from a bundle path
2. Merge this now and add the test after Adding OPM cli with registry add and rm commands #89 merges.

There is also a third option: Write a test that creates a database and populates it with the information that we need to query, but I feel that'll just be dead code soon.

What do we think is our preference here?

[ecordell]

/lgtm

That's fine, we can come back with tests after #89 merges

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