Add gradient related API

[kursatyurt]

This PR adds nearest neighbour gradient related API to python bindings

[davidscn]

Looks good overall, the documentation needs some clarification. Please apply relevant comments to all API functions (didn't look at all). The docker image has been updated. As far as I understand you can add tests now and they should work.

[kursatyurt]

@IshaanDesai @BenjaminRodenberg @davidscn Tests are ready. Since gradient data has no read API, tests are only write-type tests that checks different data structures.

[davidscn]

Since gradient data has no read API, tests are only write-type tests that checks different data structures.

How can we validate the correctness of the data passed to preCICE? Can we execute a basic integration test or access preCICE internals?

[IshaanDesai]

How can we validate the correctness of the data passed to preCICE? Can we execute a basic integration test or access preCICE internals?

I have not looked at the tests yet but in general the idea of mock testing in the python bindings is that we provide an expected output to a mocked preCICE interface and then we pass the data and compare it against the expected (correct) data already present inside the mocked preCICE interface.

[kursatyurt]

How can we validate the correctness of the data passed to preCICE? Can we execute a basic integration test or access preCICE internals?

I have not looked at the tests yet but in general the idea of mock testing in the python bindings is that we provide an expected output to a mocked preCICE interface and then we pass the data and compare it against the expected (correct) data already present inside the mocked preCICE interface.

So can I write the assertion in cpp file and expect some correct input from the test script?

[IshaanDesai]

API and tests look good now 👍 I will try to update the Spack image so that the build goes through and then we can merge this

[davidscn]

@IshaanDesai is this now ready to merge?

[IshaanDesai]

@davidscn @kursatyurt just sync with develop and then we can proceed with merging

[kursatyurt]

@davidscn @kursatyurt just sync with develop and then we can proceed with merging

Done!.