Cleanup deprecation warnings

[m-vdb]

Proposed changes:

• cleanup some old deprecation warnings
• new API to raise a deprecation warning, that requires a warn_until_version argument.
  (Original Slack thread)

Status (please check what you already did):

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

[m-vdb]

@tmbo @erohmensing this is a second pass to remove deprecation warnings and introduce a new API to raise deprecation warnings. WDYT?

[erohmensing]

Yes, this is what I had in mind!

[wochinge]

@m-vdb I won't get to this before my vacation - can you please assign somebody else for review?

[m-vdb]

sorry, completely forgot

[degiz]

That's great! 🚀

One note about Removed support for string ``responses``(use dictionaries instead).:
Let's include that in the rasa/core/schemas/domain.yml, then it will be a part of our standard domain verification!

[m-vdb]

@degiz I've implemented the changes we just talked about: keep nlu.yml the same as it doesn't need validation to go through; custom validation of "custom" and "text" keys inside of a response. Ready for review 🚀

[m-vdb]

@degiz last thing: test_nlg_fails_on_empty_response() is failing because of the changes I made in RasaYAMLReader. Should I remove the test? Why did we write it in the first place?

[degiz]

@m-vdb I've just noticed that responses are parsed as a part of NLU, it used to be a domain!

@tmbo since you've implemented the recent changes to response selector, we now have Domain::collect_templates() and RasaYAMLReader both operating on responses YAML key, was it done intentionally? Could it have be just one of the files?

[tmbo]

yes and no - it could have been a single file, but previously we required users to move the responses into their own file which made it easier to implement this in the same way.

conceptually it should be possible to combine utter templates and response selector responses, we just need to make sure they end up in the right place

[m-vdb]

@degiz from the commit on this file it looks like it was intended. The commit also introduced the changes to schemas/nlu.yml.

It looks to me that I should re-revert my changes:

• create rasa/utils/schemas.yml file
• define a partial schema for the responses key there
• reference this partial schema in both domain.yml and nlu.yml

Do you agree?

[degiz]

@m-vdb I'm sorry things are so complicated 😄
Anyway, this "split responses" topic is definitely not part of this commit, so yes, please proceed with you original change.

[m-vdb]

no problemo - good learning opportunity for me! Will push my changes

[degiz]

🚀