fix: [interoperability] Added missing interoperability flag in Observable Objects v2.1

stix2/v21/base.py

@@ -12,6 +12,9 @@ class _STIXBase21(_STIXBase):
 class _Observable(_Observable, _STIXBase21):
 
     def __init__(self, **kwargs):
+        interoperability = kwargs.get('interoperability', False)
+        self.__interoperability = interoperability
+        self._properties['id'].interoperability = interoperability
         super(_Observable, self).__init__(**kwargs)
         if 'id' not in kwargs:
             # Specific to 2.1+ observables: generate a deterministic ID