Fix OpenTelemetry dependency versions in generated Dataflow runner Maven POM

[damccorm]

Problem

Projects consuming org.apache.beam:beam-runners-google-cloud-dataflow-java:2.78.0-SNAPSHOT with Maven fail to resolve the runner's transitive dependencies because the published POM is rejected as invalid:

[WARNING] The POM for org.apache.beam:beam-runners-google-cloud-dataflow-java:jar:2.78.0-... is invalid, transitive dependencies (if any) will not be available
[ERROR] 'dependencies.dependency.version' for io.opentelemetry:opentelemetry-exporter-otlp:jar is missing.
[ERROR] 'dependencies.dependency.version' for io.opentelemetry:opentelemetry-sdk-extension-autoconfigure:jar is missing.

Because Maven skips all transitive dependencies when a dependency's POM fails model validation, required runner dependencies (such as com.google.api.services.dataflow.Dataflow) are missing at runtime, causing PipelineOptionsFactory initialization and pipeline submission to fail. This also broke the PostRelease Nightly Snapshot workflow (#30505).

Root Cause

1. Custom POM generation in BeamModulePlugin.groovy:
   • When generating <dependencies>, BeamModulePlugin only emits <version> if it.version != null on the direct dependency entry in library.java.
   • When generating <dependencyManagement>, BeamModulePlugin only imports BOMs (Category.REGULAR_PLATFORM / Category.ENFORCED_PLATFORM) that are directly declared in that subproject's implementation (or shadow) configuration.
2. Missing BOM import and versionless OpenTelemetry declarations:
   • In BeamModulePlugin.groovy, opentelemetry_exporter_otlp and opentelemetry_extension_autoconfigure (along with opentelemetry_api and opentelemetry_sdk) were declared without explicit versions (// opentelemetry-bom sets version).
   • Other modules using versionless opentelemetry_* dependencies (sdks/java/core, sdks/java/io/google-cloud-platform, sdks/java/io/kafka, sdks/java/extensions/opentelemetry-gcp-auth-extension) explicitly declare platform(library.java.opentelemetry_bom), whereas runners/google-cloud-dataflow-java/build.gradle only declared enforcedPlatform(library.java.google_cloud_platform_libraries_bom) (which does not manage opentelemetry-exporter-otlp or opentelemetry-sdk-extension-autoconfigure).
   • When Include OpenTelemetry dependencies in published Dataflow runner POM #40352 promoted opentelemetry_exporter_otlp and opentelemetry_extension_autoconfigure from runtimeOnly to implementation in runners/google-cloud-dataflow-java/build.gradle, Gradle still resolved their versions transitively via :sdks:java:core during compilation, but beam-runners-google-cloud-dataflow-java.pom was generated without <version> on those two dependencies and without opentelemetry-bom-alpha in <dependencyManagement>.

Fix

1. Import opentelemetry_bom in runners/google-cloud-dataflow-java/build.gradle: Adds implementation platform(library.java.opentelemetry_bom) and permitUnusedDeclared platform(library.java.opentelemetry_bom) (matching sdks/java/core, sdks/java/io/google-cloud-platform, sdks/java/io/kafka, and sdks/java/extensions/opentelemetry-gcp-auth-extension) so io.opentelemetry:opentelemetry-bom-alpha is imported in <dependencyManagement> of beam-runners-google-cloud-dataflow-java.pom.
2. Set explicit $opentelemetry_version on OpenTelemetry entries in BeamModulePlugin.groovy: Sets :$opentelemetry_version (kept in sync with libraries-bom by bomupgrader.py) on opentelemetry_api, opentelemetry_sdk, opentelemetry_exporter_otlp, and opentelemetry_extension_autoconfigure (following Fix pom involving maven-archetype and opentelemetry #38518 for opentelemetry_context), and removes the duplicate opentelemetry_sdk_testing map key, ensuring no module can emit a versionless OpenTelemetry dependency in its published POM.

[damccorm]

R: @stankiewicz

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.27%. Comparing base (76f6e6d) to head (5b56e4a).
⚠️ Report is 137 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #40530      +/-   ##
============================================
+ Coverage     56.16%   65.27%   +9.10%     
- Complexity     2288    13921   +11633     
============================================
  Files          1124     1720     +596     
  Lines        178336   107838   -70498     
  Branches       1489    11245    +9756     
============================================
- Hits         100170    70388   -29782     
+ Misses        75645    33265   -42380     
- Partials       2521     4185    +1664     

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