Add find_observables method

[nadouani]

Request Type

Feature Request

Problem Description

Add a find_observable method to allow searching for observables, cross cases.

[dainok]

I found that get_case_observables can be used, but it requires a case.

        # Append the custom query if specified
        if "query" in attributes:
            criteria = And(parent_criteria, attributes["query"])
        else:
            criteria = parent_criteria
        data = {
            "query": criteria
        }

Can we make case_id optional? Or should we implement a find_observables?

[nadouani]

In general, I think that adding find_observables methods is needed, because it could be helpful in many use cases.