Add API route for location introversion

[greenape]

flowmachine.features.location.location_introversion.LocationIntroversion should have an exposed API route.

I'm thinking same parameterisation as the other exposed routes - start, stop, aggregation unit + direction, but I'd like direction to be optional with default both.

• Add LocationIntroversionExposed class
• Add marshmallow schema
• Add schema to FlowmachineQuerySchema
• Add flowclient function
• Add tests to integration tests
  • Add test case to test_get_query_params
  • Add test case to test_run_query
• Add query endpoint to Flowauth demo data
• Update approval test data for integration tests

[maxalbert]

Thinking about it, the purpose of the integration tests test_get_query_params and test_run_query (in the files integration_tests/tests/flowmachine_server_tests/test_action_get_params.py and integration_tests/tests/flowmachine_server_tests/test_action_run_query.py) is to exercise the respective action handlers but should be agnostic of any specific queries.

Instead, if we want to test the specific queries and their parameters I suggest to add a test to integration_tests/tests/test_queries.py, which exercises the individual queries through their respective flowclient functions.

At the moment the test files and test names don't always make it very clear what their purpose is and which parts of the code they are supposed to exercise. We should rename the above ones in particular to clarify this. I have opened #584 to track this.