* [dart-dio] Add basic integration test POM
This basically just fetches dependencies, runs the built_value generator and empty test cases. Even running empty test cases is more than is currently possible and at least finds compile errors.
There are compile errors atm which need to be fixed.
* [dart-dio] Fix missing BuiltSet import in models that use enums
* [dart-dio] Fix compile error when the return type is a Map
* the compile error was `serializerForType(Map<String, int>)` in `StoreApi` which needs to be `serializerForType(Map)`
* use final instead of var in response handling
* [dart-dio] Generate docs after changes
* [dart-dio] Add integration test to CI execution list