rasa data validate should fail if conflicting slots are created in different domain files

[hsm207]

What problem are you trying to solve?

Users may split the domain.yml into multiple files and have different teams work on different domain.

I want rasa data validate to check and fail if there are duplicate intents, conflicting slots, etc across the split domain files.

For example:

1. Run rasa init.
2. Copy domain.yml to domain/domain1.yml.
3. Delete domian.yml
4. Add the following slots in domain/domain1.yml:
   
5. Create an empty file at domain/domain2.yml and write:
   
6. Run rasa data validate -d domain/.

The check will complete without errors

What's your suggested solution?

rasa data validate consolidates all the domain files and then runs the yaml validation check.

Examples (if relevant)

No response

Is anything blocking this from being implemented? (if relevant)

No response

Definition of Done

• rasa data validate -d domain/ does not fail when conflicting/duplicate slots/intents/etc are found
• Add an integration test to ensure this works as expected
• Fixed merged into 2.8 and 3.0

[TyDunn]

The fix for this issue will need to be backported to the last minor of the previous major (i.e. Rasa Open Source 2.8)