Add 'type' field to ExperimentParametersModel

This commit introduces a new 'type' field in the ExperimentParametersModel schema and updates the associated code in `sample.py` to include this field during object creation. Additionally, unnecessary lines and redundant code in `testfunctions.ipynb` have been removed for better readability and maintainability.

backend/app/routers/sample.py

@@ -334,6 +334,7 @@ def create_experiment_parameters_for_sample(
     # stored as JSON.
     new_exp = ExperimentParametersModel(
         run_number=new_run_number,
+        type=exp_params.type,
         beamline_parameters=exp_params.beamline_parameters.dict()
         if exp_params.beamline_parameters
         else None,