Revise openapi-generator build process to be more sustainable into the future

[jordanpadams]

💡 Description

Per #14, we are using a forked version of the openapi-generator code in order to fix and issue with handling arrays vs. single values as they are returned from parts of the API. We need to come up with a more sustainable solution using the production openapi-generator.

[jimmie]

FYI - the version of openapi-generator installed by homebrew continues to demonstrate the issue identified and addressed by Thomas' fork. Attempts to build the fork as well as the main branch of the OpenAPITools fail at identical points, first on javadoc warnings then after modifying the pom to not fail out on javadoc warnings, in the regression tests (e.g. error building the Ping project). However, I ran the docker version as documented here: https://hub.docker.com/r/openapitools/openapi-generator-cli/ and it produced the python code from the 1.1 version of the preprocessed swagger spec without error (still need to test it however). Once tests are completed, I will update the documentation accordingly, then we can consider closing this issue.