Documentation for extra_params for the oracle provider.

[Moritz-Langer]

Overview

Documentation on the extra_params variable in the oracle provider and the reasoning behind it was suggested by @doublebyte1 in #1673.

Added the documentation and an example use case for the extra_params variable..

Related Issue / discussion

See discussion under
#1673
and potentially related issue
#2071 (introduction of include_extra_query_parameters)

Additional information

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