Support pulling OCI Image Index manifests

[rquinio]

Resolves #2749

Implementation follows #3700 (comment)

• Add Accept header application/vnd.oci.image.index.v1+json during base image pull
• Re-use the logic from V22ManifestListTemplate to select the target platform diget via a new interface ManifestListTemplate

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[elefeint]

@rquinio Thank you; we'll review next week.

[elefeint]

The PR looks very good; I apologize for the delay.

Could you run ./gradlew goJF to reformat the code (details? That should fix the code coverage by allowing tests to run.

[rquinio]

No worries. Hopefully I've fixed the formatting issue.

[elefeint]

Could you add tests for:

1. AbstractManifestPuller.getAccept() returning the correct media type for OciIndexTemplate.class
2. `AbstractManifestPuller.getManifestTemplateFromJson() returning the right thing

Thank you!

[rquinio]

Done ! I also took the opportunity to fix missing coverage in PullBaseImageStep for manifest lists pulling and case where the target architecture is not in the list.

[elefeint]

Test failure:

> Task :jib-core:test

com.google.cloud.tools.jib.builder.steps.PullBaseImageStepTest > testCall_allMirrorsFail FAILED
    java.lang.NullPointerException
        at com.google.cloud.tools.jib.builder.steps.PullBaseImageStep.pullBaseImages(PullBaseImageStep.java:296)
        at com.google.cloud.tools.jib.builder.steps.PullBaseImageStep.call(PullBaseImageStep.java:159)
        at com.google.cloud.tools.jib.builder.steps.PullBaseImageStepTest.testCall_allMirrorsFail(PullBaseImageStepTest.java:571)

com.google.cloud.tools.jib.builder.steps.PullBaseImageStepTest STANDARD_OUT
    [MockitoHint] PullBaseImageStepTest.testCall_allMirrorsFail (see javadoc for MockitoHint):
    [MockitoHint] 1. Unused... -> at com.google.cloud.tools.jib.builder.steps.PullBaseImageStepTest.setUpWorkingRegistryClientFactoryWithV22ManifestList(PullBaseImageStepTest.java:672)
    [MockitoHint]  ...args ok? -> at com.google.cloud.tools.jib.builder.steps.PullBaseImageStep.pullBaseImages(PullBaseImageStep.java:294)

[rquinio]

Should be fixed, testCall_allMirrorsFail was wrongly using the client factory with new V22ManifestList mocks, instead of the old V22ManifestTeplate mock.

[elefeint]

@rquinio Thank you! I'm afraid we need a bit more testing to pass the 80% coverage gate. OciIndexTemplate.ManifestDescriptorTemplate is likely an easy candidate. Can you see the Sonar report that's linked in "Details" under the Github Action checks?

[rquinio]

@elefeint I've added a test for POJO -> JSON serialization.
I had a look at the code duplication, but I wouldn't risk factorizing the JSON objects between docker and OCI manifests as they have different fields, and I'm not sure of the details of each spec.

[elefeint]

Thanks! I agree that the two formats could easily diverge in the future.

[sonarcloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
2 Code Smells

95.2% Coverage
4.5% Duplication