[python] fixes bugs

[spacether]

fixes bugs in 6.2.0

• Generator generating reserved word ("from") for $refed properties
• Attribute error when using auth header
• generator ignores global-property settings
• python client fails to properly deserialize using discriminator (use nonCompliantUseDiscriminatorIfCompositionFails)
• Regex patterns without trailing slashes break Python client generation

I am adding these fixes here so users who use the python client have fully working code.
Later when this generator is replaced, users of this generator will need to get it from https://github.com/openapi-json-schema-tools/openapi-json-schema-generator which also includes these fixes.

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh
  

  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  For Windows users, please run the script in Git BASH.
• File the PR against the correct branch: master (6.1.0) (minor release - breaking changes with fallbacks), 7.0.x (breaking changes without fallbacks)
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.