[#95] Mark build-bom mojo as thread safe

[rhusar]

Allows the plugin to run in parallel builds (-T) without Maven emitting the "not marked @threadsafe" warning and degrading to serial execution.

Audited the mojo for the usual parallel-build hazards:

• No static mutable state. The only static members are the WILDCARD constant and the ModelWriter nested class.
• Mojo instances are created per execution, so all @parameter and @component fields are thread confined. This covers the in-place mutation of configuration objects in initializeModel() (parent version) and resolveDependency() (includeDependencies entries).
• addDependencyManagement() operates on mavenProject.clone(), and MavenProject.deepCopy() clones the underlying Model, so the reactor's MavenProject is never mutated when the resolver project's dependencies and dependency management are rewritten.
• addBuilderManagedDependency() clones each source dependency before changing its version, scope or exclusions, so the source project's dependency management list is not modified in place.
• The injected components (ProjectDependenciesResolver, RepositorySystem, ProjectBuilder, ArtifactHandlerManager) are Maven singletons intended for concurrent use; repositorySystemSession and repositories are only read.
• MavenProject and MavenSession are injected through the mojo execution scope, which is backed by a ThreadLocal, so each thread gets its own instances.
• The BOM is written to the project's own build directory, so concurrent reactor modules cannot write the same file.
• OrderedProperties is documented as not thread safe, but a fresh instance is created per execution and never escapes the thread.
• The one remaining write to state shared between threads is MavenSession.getProjectBuildingRequest(), which lazily creates and then mutates the single ProjectBuildingRequest owned by the MavenExecutionRequest. That happens inside Maven core, every thread writes the same repository session, and the result is immediately copied into a new DefaultProjectBuildingRequest before use.

[emmartins]

Looks good, may I just ask you to create an issue for this change at https://github.com/wildfly/wildfly-bom-builder-plugin/issues ?

[rhusar]

Ok will do.

[rhusar]

Looks good, may I just ask you to create an issue for this change at https://github.com/wildfly/wildfly-bom-builder-plugin/issues ?

Done #95 and linked. 👍🏼