Oracle Connection Pooling implementation of issues/1655

[Moritz-Langer]

Overview

This is an implementation of connection pooling in oracle. It leaves the decision up to the environment, if the variables
ORACLE_POOL_MIN and ORACLE_POOL_MAX are found in the environment, a Pool is created with min and max connections according to the variable values. If they are not set, than single connections are used, just like before.
This should lead to no breaks for current users and is easy to set up.

Tests and Documentation are added as well.

Related Issue / discussion

Related to #1655

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

[Moritz-Langer]

@8luewater fyi

[tomkralidis]

Requesting a few minor changes -- good work!

[Moritz-Langer]

Hi Tom,
thank you for the feedback and the review. I have adjusted according to your comments.