Docker: add env var to enable building OpenAPI document with invalid collections (#2188)

[tomkralidis]

Overview

This PR enables OpenAPI generation in Docker mode to skip invalid collections, thereby allowing for OpenAPI generation to complete as part of entrypoint execution. Docker documentation updates are also included.

cc @KoalaGeo

Related Issue / discussion

Fixes #2188

Additional information

Default behaviour is consistent with pygeoapi openapi generate (fail on first invalid collection).

Dependency policy (RFC2)

• I have ensured that this PR meets RFC2 requirements

Updates to public demo

• I have ensured that breaking changes to the pygeoapi master demo server have been addressed
  • https://github.com/geopython/demo.pygeoapi.io/blob/master/services/pygeoapi_master/local.config.yml

Contributions and licensing

(as per https://github.com/geopython/pygeoapi/blob/master/CONTRIBUTING.md#contributions-and-licensing)

• I'd like to contribute [feature X|bugfix Y|docs|something else] to pygeoapi. I confirm that my contributions to pygeoapi will be compatible with the pygeoapi license guidelines at the time of contribution
• I have already previously agreed to the pygeoapi Contributions and Licensing Guidelines

[tomkralidis]

CI failures are unrelated.