Raising exception when having empty intent or entity mapping in the domain

[Imod7]

Proposed changes:

• Added an InvalidDomain exception when having an empty intent/entity mapping in the domain.yml file.

Status (please check what you already did):

• added two tests for the functionality
• updated the documentation
• updated the changelog (please check changelog for instructions)
• reformat files using black (please check Readme for instructions)

[alwx]

Approved but please take a look at the two small comments I've left :)

[Imod7]

Hi @alwx ! Thank you so much for your review and constructive feedback! Please let me know if any further rewording is needed in the docstring or the exception.

After making the current changes for the empty intent mapping, I also thought that a user might also insert an empty entity mapping so in the domain.yml file maybe we get something like this :

entities:
  - cuisine:

instead of the correct one :

entities:
  - cuisine

and the error we get when having the empty entity mapping is the following :

TypeError: argument of type 'NoneType' is not iterable

I checked the code and saw that if I add a check here, then instead of the error I can raise another InvalidDomain exception message.
Should I add this check? If yes, should I do it in the current PR or open a new Issue ?
Thank you so much for your time!!! 🙏🏽

[alwx]

Since it's a small change and because it's related to what you've done here, then I think it's perfectly fine to do it in the same PR. Don't forget to update the changelog entry in this case! :)

[wochinge]

@joejuzl Do you have time for another quick review so this PR can get wrapped up?

[joejuzl]

LGTM