[FEATURE] Add simple self_test to Python API

[mgovers]

Some users may want to do a simple check to see if the installation was successful and there are no build errors, segfaults, undefined symbols, ...

This will enable users to build + verify the python library using pip install in the case there are no prebuilt binaries available.

This should not be part of the postinstall script, but indeed should be called by a user by running e.g.

from power_grid_model.utils import self_test

self_test()

Design

• to src/power_grid_model.utils, add a function def self_test() without arguments. The test should run the following things:
  • with clause setting up a temporary directory for IO of the test (using standard Python temporary directory functionality)
    • Create a simple JSON input data file in the temporary directory:
      • 1 nodes, 1 source, 1 load
      • The written data should be in the PGM serialization schema
    • Load the created JSON input data file (deserialize)
    • Create a PowerGridModel instance from the loaded input data
    • Run a simple power flow calculation on the created model
      • linear calculation method should be sufficient
    • Write the calculation result to a file in the temporary directory
      • Use the json_serialize_to_file functionality
    • Verify that the written output is correct
  • Clean up the temporary directory (end of with clause)

This does multiple C API calls, runs through the main data flow, and verifies integrity of (de)serialization.