Check only existing processes are mapped

[sophieherrmann]

There should be some kind of check whether a created openeo-processes-python call actually exists and can be executed.

As a first version all process names supported in openeo-processes-python could be hard coded.

In a second step also the parameters should be checked.

https://github.com/Open-EO/openeo-processes-python

[danielFlemstrom]

Maybe this should rather be done in the process_discovery endpoint of OpenEO-API to avoid direct dependencies between the repositories? At RISE, we implemented the checkup something like shown below, maybe you want to cache the process-list (we do this in the calling function to avoid unnecessary http traffic).
IMHO, I think the proper way would be to implement something like get_implemented_process_defsin openeo-processes-python to avoid using dir on openeo_processes....