[BUG][python] ClassCastException on specific configuration variables of python-flask generator

[MiltiadisKoutsokeras]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

Using any of the following configuration variables with python-flask generator results in the following error:

Exception in thread "main" java.lang.ClassCastException: class java.lang.Boolean cannot be cast to class java.lang.String (java.lang.Boolean and java.lang.String are in module java.base of loader 'bootstrap')
	at org.openapitools.codegen.languages.AbstractPythonConnexionServerCodegen.processOpts(AbstractPythonConnexionServerCodegen.java:191)
	at org.openapitools.codegen.DefaultGenerator.configureGeneratorProperties(DefaultGenerator.java:251)
	at org.openapitools.codegen.DefaultGenerator.generate(DefaultGenerator.java:877)
	at org.openapitools.codegen.cmd.Generate.execute(Generate.java:441)
	at org.openapitools.codegen.cmd.OpenApiGeneratorCommand.run(OpenApiGeneratorCommand.java:32)
	at org.openapitools.codegen.OpenAPIGenerator.main(OpenAPIGenerator.java:66)

Configuration Variables:

• featureCORS
• testsUsePythonSrcRoot
• useNose
• usePythonSrcRootInImports

According to config-help --generator-name python-flask output these all should be boolean.

openapi-generator version

Latest Docker image

openapi-generator-cli 6.0.0-SNAPSHOT
  commit : 6f37409
  built  : 2022-03-10T08:57:57Z

OpenAPI declaration file content or url

openapi: "3.0.3"

info:
  title: Test python-flask generator
  version: "1.0.0"

paths:
  /test:
    get:
      responses:
        "200":
          description: OK

Generation Details

Using this configuration file

additionalProperties:
  featureCORS: false
  testsUsePythonSrcRoot: false
  useNose: false
  usePythonSrcRootInImports: false

And launching the Docker image:

docker run --name "openapi-generator-cli" --rm -u $(id -u ${USER}):$(id -g ${USER}) --mount type=bind,src=$(pwd),dst=/host openapitools/openapi-generator-cli:latest generate --input-spec /host/openapi/openapi.yaml --generator-name python-flask --config /host/openapi/python-flask-config.yaml --output /host/output/python-flask/ --verbose

Keeping any value in the configuration file still reproduces the problem.

Steps to reproduce

Just follow the steps above.

Related issues/PRs

Have not found any.

Suggest a fix

Nothing.