issue #693 add search for schema and find parameters from the backend

[ElienVandermaesenVITO]

#693

[soxofaan]

In this PR you add a lot of utility functions. A couple of notes on that:

• they are al public at the moment, so adding them adds the burden to keep/maintain/support them. In that sense, they should also get good test coverage.
• some of the seem quite tailored for the specific use case of this PR, while they are named very generically

also note that we already have parsing functionality for process definitions: e.g. see starting point openeo.internal.processes.Process.from_dict(). I think that should eliminate the need for all these new utility functions

I think it's also important that the core goal of this PR gets unit tests coverage

[ElienVandermaesenVITO]

The test fail because of No mock address: GET https://oeo.test/processes. Do I have to change the test and add the address or is there another way to solve it?

[soxofaan]

this feature indeed impacts existing tests

FAILED tests/rest/datacube/test_datacube100.py::test_sar_backscatter_defaults - requests_mock.exceptions.NoMockAddress: No mock address: GET https://oeo.test/processes
FAILED tests/rest/datacube/test_datacube100.py::test_sar_backscatter_custom - requests_mock.exceptions.NoMockAddress: No mock address: GET https://oeo.test/processes
FAILED tests/rest/datacube/test_datacube100.py::test_sar_backscatter_coefficient_none - requests_mock.exceptions.NoMockAddress: No mock address: GET https://oeo.test/processes
FAILED tests/rest/datacube/test_datacube100.py::test_sar_backscatter_coefficient_invalid - requests_mock.exceptions.NoMockAddress: No mock address: GET https://oeo.test/processes

doing cube.sar_backscatter() now triggers a GET /processes request, so you should indeed add a mock for that in these tests

[ElienVandermaesenVITO]

Moved this function to util.py, because it couldn't be imported from connection.py due to a circular import issue. Can it stay here or should it be moved elsewhere @soxofaan