Filtering for data type "boolean"

[uwerauschenbach]

Problem description
In clause 8.3,, filtering for data of types "Text", "Number" and "Dates" is defined.
Filtering for "Boolean", even though also a type of values in JSON, is missing.

Expected action
Add indications how to formulate filter criteria for boolean-valued attributes.
To be discussed whether we use comparison i.e. "boolAttr=true&..." and "boolAttr=false&..." or flag notation i.e. something like "boolAttr&..." for true and "boolAttr.not&..." for false

Additional context
None.