categorical slot should have category other so that other values could be mapped to it

[Ghostvv]

Rasa Core version: master

Python version: 0.3.6

Operating system (windows, osx, ...): macOS

Issue:
Right now categorical slot requires to name its all possible values in domain.yml, though for practical reasons it is convenient to have general category like other, to which all values not mentioned in the list are mapped

Content of domain file (if used & relevant):

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[wochinge]

Makes sense to me 👍 Should we remove the discussion label?

[Ghostvv]

if it makes sense to do, then we can consider it to be discussed 😀

but then I would allow to create a slot with only one category, then effectively it'll become two categories due to addition of other

[indam23]

should there be any warning for values mapped to other? and what should happen if someone puts a literal "other" as a value in the domain?

[indam23]

@Ghostvv