Throw if @Comment and registerComments use the same path for a comment

[ljacqu]

Currently, if @Comment on a property and some statement in SettingsHolder#registerComments set the comments for the same path, one of the comments is just discarded. This is misleading, and should be prevented by throwing an exception. There's no use case to defining part of the comment in the annotation or in the method—one approach should be used per path.

To do

• Change CommentsConfiguration to throw an exception if a comment is registered to a path that already has comments
• Add unit tests

Hint

• Map#put returns the old value for the same key if it existed, i.e. if it's not null, a comment already existed!

[sharief007]

We can use Map#containsKey to check if the path is already mapped to a list of comments before throwing the exception. However, this approach may not allow us to overwrite an existing path. It seems the CommentsConfiguration#setComment should allow overriding the paths. Hence as mentioned in the issue description Map#put is used to check.

Pull Request: https://github.com/AuthMe/ConfigMe/pull/373