Issue #2281111: Porting 'Entity is of bundle (entity_is_of_bundle)' cond...

...ition to 8.x

See: d.o issue #2281111 - https://drupal.org/node/2281111
This creates an EntityIsOfBundle condition and an associated test that checks a simulated node entity's type and bundle.
OK, cool. I'm not familiar with constraints, but the concept makes sense. It looks like this is the authoritative reference for available constraints: https://api.drupal.org/api/drupal/namespace/Symfony%21Component%21Validator%21Constraints/8
What constraints would be relevant here? "NotBlank"...or "NotNull" may be relevant for all three. "Type" seems redundant. "Length" would make sense for the strings...