Add `service` link to individual processes

[fmigneault]

Description

Add service link to individual processes.

As indicated by opengeospatial/ogcapi-processes#466, the service relation of links returned by respective processes are recommended to be returned by pointing to the landing page of the service (aka, weaver.wps_rest_api_url).

To Do

• add the relevant service link to processes responses links (JSON and headers)
• add the /rec/ogc-process-description/process-links to conformances listing.

References

• Add service link recommendation. opengeospatial/ogcapi-processes#466