Validating a process execution document without yet executing the process

In the context of building a bridge between our server supporting the Workflows extension with a core OGC API - Processes, we realized it would be very useful to validate the submission of a process execution document without actually triggering the processing.

This could be as simple as introducing a "mode" : "validate", and would allow the server to validate all inputs, and if successful return the list of outputs (without actual data) that would have been returned if the process was executed. This may also be related to the Quotation extension (e.g. "mode" : "quotation").

In the proposed Workflows extension, a workflow involving one or more processes can first be validated along the full chain to make sure it will work, before requests can be issued for specific AoI+resolution. Supporting this would allow to implement this bridge while properly validating processes from APIs not supporting the Workflows extension, used as part of such a workflow.