[REQ] A configuration of the JUnit version used for the tests produced by the Java generator

Is your feature request related to a problem? Please describe.

We are using the Java generator in order to access other REST resources. The generated code also produces JUnit tests (a nice feature to keep our test coverage threshold) but they are designed to use the JUnit 4 library. In our case we only use JUnit 5. At the moment there is no possibility to configure this.

Describe the solution you'd like

The openapi-generator-maven-plugin has already the configuration to turn off the API tests and Model tests (configuration parameters: generateApiTests and generateModelTests). Another configuration to determine the utilized JUnit library in these tests would be nice.

Describe alternatives you've considered

Maybe to supersede the default case of now using JUnit 5 instead of the old JUnit 4 library.

Additional context

In the beginning I have asked at Stackoverflow to get some help and somone mentioned to create a Feature Request here:
https://stackoverflow.com/questions/76920305/generated-test-classes-use-junit-4

Start with the openapi-generator-maven-plugin configuration and its existing generateApiTests and generateModelTests parameters. Trace how the Java generator produces API and model test classes and identifies their JUnit dependency. Done means generated tests can use a selected JUnit library, including JUnit 4 and JUnit 5, without breaking the existing test-generation options.