Mojo not marked as thread-safe

[abentele]

Describe the bug

When using parallel execution of maven, this message is printed:

[WARNING] *****************************************************************
[WARNING] * Your build is requesting parallel execution, but project      *
[WARNING] * contains the following plugin(s) that have goals not marked   *
[WARNING] * as @threadSafe to support parallel building.                  *
[WARNING] * While this /may/ work fine, please look for plugin updates    *
[WARNING] * and/or request plugins be made thread-safe.                   *
[WARNING] * If reporting an issue, report it against the plugin in        *
[WARNING] * question, not against maven-core                              *
[WARNING] *****************************************************************
[WARNING] The following plugins are not marked @threadSafe in [...]:
[WARNING] io.openapitools.swagger:swagger-maven-plugin:2.1.6
[WARNING] Enable debug to see more precisely which goals are not marked @threadSafe.
[WARNING] ***************************************************************

To Reproduce

use command mvn clean install -T2C to build a multi-module project.

Expected behavior

If the mojo is thread-safe it should be marked as thread-safe (via org.apache.maven.plugins.annotations.Mojo#threadSafe which defaults to false).

Additional context

Nothing.