Egeria 'platform' definition from gradle isn't usable

[planetf1]

When building connectors, one useful technique is to set dependency constraints using the versions we have for core egeria.

This helps keep dependencies aligned, and reduces the risk of classpath clashes whilst avoiding having to manual keep versions in place.

This can be done in the consumer of egeria using either

implementation platform org.odpi.egeria:egeria:4.0-SNAPSHOT

or

implementation enforced platform org.odpi.egeria:egeria:4.0-SNAPSHOT

More info at https://docs.gradle.org/current/userguide/platforms.html#sub:platforms-vs-catalog

This is similar to an 'import' scope dependency in maven

With the migration to gradle, an attempt to update the xtdb 4.0 connector to use the platform definition failed with:

* What went wrong:
Could not determine the dependencies of task ':egeria-connector-xtdb:withDependencies'.
> Could not resolve all files for configuration ':egeria-connector-xtdb:runtimeClasspath'.
   > Could not resolve org.odpi.egeria:egeria:4.0-SNAPSHOT.
     Required by:
         project :egeria-connector-xtdb
      > No matching variant of org.odpi.egeria:egeria:4.0-SNAPSHOT:20230221.172710-30 was found. The consumer was configured to find a runtime of a platform compatible with Java 17, packaged as a jar, preferably optimized for standard JVMs, and its dependencies declared externally but:
          - Variant 'apiElements' capability org.odpi.egeria:egeria:4.0-SNAPSHOT declares a component compatible with Java 17, packaged as a jar, and its dependencies declared externally:
              - Incompatible because this component declares an API of a library and the consumer needed a runtime of a platform
              - Other compatible attribute:
                  - Doesn't say anything about its target Java environment (preferred optimized for standard JVMs)
          - Variant 'javadocElements' capability org.odpi.egeria:egeria:4.0-SNAPSHOT declares a runtime of a component, and its dependencies declared externally:
              - Incompatible because this component declares documentation and the consumer needed a platform
              - Other compatible attributes:
                  - Doesn't say anything about its target Java environment (preferred optimized for standard JVMs)
                  - Doesn't say anything about its target Java version (required compatibility with Java 17)
                  - Doesn't say anything about its elements (required them packaged as a jar)
          - Variant 'runtimeElements' capability org.odpi.egeria:egeria:4.0-SNAPSHOT declares a runtime of a component compatible with Java 17, packaged as a jar, and its dependencies declared externally:
              - Incompatible because this component declares a library and the consumer needed a platform
              - Other compatible attribute:
                  - Doesn't say anything about its target Java environment (preferred optimized for standard JVMs)
          - Variant 'sourcesElements' capability org.odpi.egeria:egeria:4.0-SNAPSHOT declares a runtime of a component, and its dependencies declared externally:
              - Incompatible because this component declares documentation and the consumer needed a platform
              - Other compatible attributes:
                  - Doesn't say anything about its target Java environment (preferred optimized for standard JVMs)
                  - Doesn't say anything about its target Java version (required compatibility with Java 17)
                  - Doesn't say anything about its elements (required them packaged as a jar)

This needs to be addressed so that we have a good platform definitions that consumers can use, and is a critical need for version 4 release

[planetf1]

It looks like some refactoring is needed to make use of the 'java-platform' plugin, and very explicitly create the BOM, then consuming it in subprojects, RATHER than just declaring constraints as is done currently.

[planetf1]

fyi @mandy-chessell

[planetf1]

Tested with PR (above)

• local build of xtdb connector (with ref to oss snapshot rep replaced with local) now appears to pick up the egeria project BOM without error.
• further tests will be made once merged (it's tricky to get this totally correct in one go, with interdependencies between projects)

[planetf1]

Re-opening as testing is needed now the initial code change is in.

[planetf1]

The egeria BOM should now be correct. any problems will be raised as new issues