Consistency checks for custom filters in Mistral vs StackStorm (ActionChains)

[Mierdin]

StackStorm/st2mistral#30 copies a large number of the existing custom filters that currently exist in st2 and makes them available in Mistral as well. To limit interdependency, these were fully re-implemented in st2mistral, rather than rely on st2common in this repo.

However, this means that any changes will have to be implemented in both places, to ensure a consistent user experience (users that become familiar with a filter in one area will come to expect that it will be available in the other, which is reasonable, and the reason for StackStorm/st2mistral#30). It would be nice if we could figure out a way - probably during st2 integration test time - to ensure that the custom filters available in each place are equivalent.

I added the "under discussion" label because the right answer may just be "it's not worth the effort", which I admit, it may not be (StackStorm/st2docs#552 updates teh docs with a notice to keep the two in sync manually for the time being, and this may be good enough) - but it's good to have the discussion.

[nmaludy]

@Mierdin would it make sense to have a new package (maybe called st2jinja) where the Jinja filter code could live? I'm not sure if this is even technically possible due to dependencies.

[m4dcoder]

Addressed at #3565 and StackStorm/st2mistral#30.