BaseGenerator: Verify & Align configuration options work to with properties

[rohanKanojia]

Description

Related to #1462

BaseGenerator seems to have some common configuration options which are applicable to all generators:

https://github.com/eclipse/jkube/blob/0401297d4bcea783a94fc178af376c7a8a5a185d/jkube-kit/generator/api/src/main/java/org/eclipse/jkube/generator/api/support/BaseGenerator.java#L59-L79

Since these are generator configuration fields, they should be accessible via regular generator configuration properties i.e jkube.generator.$generatorName.name.

However, these fields are also accessible via these properties:

• name jkube.generator.name
• alias jkube.generator.alias
• from jkube.generator.from
• fromMode jkube.generator.fromMode
• registry jkube.generator.registry

This is due to a method getConfigWithFallback which checks system and project properties with given key for config field value:

https://github.com/eclipse/jkube/blob/0401297d4bcea783a94fc178af376c7a8a5a185d/jkube-kit/generator/api/src/main/java/org/eclipse/jkube/generator/api/support/BaseGenerator.java#L185

There is one field add which doesn't seem to be accessible via this method. We need to decide whether we want to align it with rest of the options or remove these additional properties.

[manusa]

This should be applicable too for the new tags config option, unless it gets directly addressed in #1462 (not at the moment).