P3-Workflows: Re-usable components ($ref with JSON Pointers)

Possibly as a separate conformance class, it would be very useful to support re-usable components with $ref and a JSON Pointer to avoid repeating the same redundant (potentially complex) nested process definition within a workflow.
In addition, an implementation would easily be able to identify that two nested process objects are identical and therefore their outputs should be re-used (as opposed to executing it twice).

This would also facilitate defining a nested process that generates multiple outputs, then refer to it adding an {"outputs": ... section to select a specific output for its use as a particular input e.g.,

{
   "process": "https://example.com/ogcapi/processes/SomeProcess",
   "inputs" : {
      "orthoPhoto" : { "$ref" : "#/components/photogrammetry", "outputs" : { "orthoPhoto": { } },
      "pointCloud" : { "$ref" : "#/components/photogrammetry", "outputs" : { "pointCloud": { } }
   },
   "components" :
   {
      "photogrammetry":
      {
         "process": "https://example.com/ogcapi/processes/Photogrammetry",
         "inputs" : { ... }
      }
   }
}

See also scenario 4 in https://github.com/opengeospatial/ogcapi-processes/issues/279#issuecomment-1046682392 , where it is used in a different context (which may be better addressed with a mechanism as part of the Input/Output Fields conformance class to aggregate over a temporal dimension for multiple intervals, as opposed to completely reducing the temporal dimension).

Start with issue 304 and scenario 4 in the linked comment on issue 279. Compare the proposed $ref and JSON Pointer component reuse with the alternative involving the Input/Output Fields conformance class. Done means the project has a decided scope and documented conformance requirements for this proposal.