Implement example process

[fmigneault]

Description

• In order to allow testing the API, the EchoProcess should be implemented.
• This should be implemented as test process in Weaver
  (update and reuse https://github.com/crim-ca/weaver/blob/master/weaver/processes/wps_testing.py)
• Update CI tests making use of the wps_testing.WpsTestProcess process that will break after modification
• Update CI tests to ensure the new set of inputs/outputs work with EchoProcess
• Docs could include the results/outputs of requests from this process for further examples/references.
  • provide the JSON payloads in the RST docs (use literalinclude)

References

• EchoProcess description:
  • under https://docs.ogc.org/is/18-062r2/18-062r2.html#toc37 (8.2. OGC process description)
    just above https://docs.ogc.org/is/18-062r2/18-062r2.html#toc38 (9. Requirements classes for encodings)
  • https://github.com/opengeospatial/ogcapi-processes/blob/24e0e17b4d6773aa856500f395109f29e92f00c7/core/examples/json/ProcessDescription.json
• SWG needs to consider the nuts and bolt of the testability of the API opengeospatial/ogcapi-processes#157

Related Issues

• Support of BoundingBox I/O #51
• Support I/O literal with unit of measure #430