NUTCH-2931 Create OpenAPI specification for Nutch 1.x REST API

[lewismc]

This is a WIP I had on an old laptop and never pushed to my public Nutch mirror. My notes are that the OpenAPI spec didn't comply with the IBM/openapi-validator which is what I use(d) to lint and validate the OpenAPI specifications I work(ed) on over the years. I didn't have enough time/was side tracked by something or lots of other somethings and ultimately forgot about this branch altogether. I was surprised to find it.
I remember using the existing Java annotations and the Wiki documentation as resources for the OpenAPI. A few ex-colleagues also assisted in developing this branch.
It needs peer reviewed for completeness and updated to OpenAPI 3.1.X however this is a good foundation.
You can view the OpenAPI documentation if you copy and paste the content into https://editor.swagger.io/.
The goal would be to use the OpenAPI Generator project to generate a server implementation we could package either with Nutch or separately altogether.
I'm open to suggestions.

[lewismc]

I pushed a commit to add a new step to lint and validate openapi.yaml. I knew this would fail but it demonstrates where I got to last time around! Addressing the issues is non-trivial work.

  Total number of errors   : 89
  Total number of warnings : 315

In an API-first development model, these items would be addressed before we do anything further.

[lewismc]

I put some more work into this PR and feel it is now ready for review. Here's a summary of the changes:

• The OpenAPI 3.1.2 specification (openapi.yaml) describing all 24 REST endpoints of the Nutch service, with HTTP/HTTPS server URL variables, HTTP Basic Authentication, and fully typed request/response schemas
• Integrate the IBM OpenAPI Validator into the master CI build (.github/workflows/master-build.yml) with a dorny/paths-filter gate so it runs only when openapi.yaml or .spectral.yaml change
• Add a .spectral.yaml ruleset override to disable IBM-specific convention rules that conflict with the existing Nutch wire format (camelCase properties, UPPER_CASE enums, bare-array responses). This means minimal code changes to the Deprecated Nutch service code. I saw this as unproductive effort if we are just going to remove it in a future version. Should we wish to create a new service based on the openapi specification we could likely reuse some of this code but that is an entirely separate effort
• Deprecate all Java classes in org.apache.nutch.service and its sub-packages with @Deprecated annotations and @deprecated Javadoc tags indicating the service will be removed in a future version of Nutch
• Add a deprecation warning to the startserver command in src/bin/nutch and mark it as deprecated in the usage text
• Mark Docker BUILD_MODE=1 (server) and BUILD_MODE=2 (server + webapp) as deprecated in docker/Dockerfile with build-time warnings
• Annotate the 6 service-only dependencies in ivy/ivy.xml (5 Apache CXF artifacts and jackson-jaxrs-json-provider) with XML comments noting they will be removed with the service

[sonarqubecloud]

Quality Gate failed

Failed conditions
56.3% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud