API provide IAnnotatedElement getter for all model xxSpec classes

[remkop]

Discussion in #1718 showed that it may be useful if the API for each xxSpec class (CommandSpec, OptionSpec, ArgGroupSpec, etc) had a getAnnotatedElement method that would return the IAnnotatedElement for that xxSpec instance.

If the xxSpec instance was created programmatically, not from an annotation, then this method would return null.

[siilike]

Just to clarify, when having something like:

@RequiredExclusive
@CommandLine.ArgGroup(multiplicity = "1", exclusive = true, validate = false)
GroupOpts group = new GroupOpts()

the IAnnotatedElement would correspond to the group field, so groupSpec.getAnnotatedElement().getAnnotation(RequiredExclusive.class) would return the RequiredExclusive annotation defined for the group field.

Also, IAnnotatedElement doesn't seem to have a method to get all defined annotations.

[remkop]

Just to clarify, when having something like:

@RequiredExclusive
@CommandLine.ArgGroup(multiplicity = "1", exclusive = true, validate = false)
GroupOpts group = new GroupOpts()

the IAnnotatedElement would correspond to the group field, so groupSpec.getAnnotatedElement().getAnnotation(RequiredExclusive.class) would return the RequiredExclusive annotation defined for the group field.

Yes, that matches my understanding.

Also, IAnnotatedElement doesn't seem to have a method to get all defined annotations.

Okay, good point, so the IAnnotatedElement interface may need an additional method like getAnnotations.