[Groovy] Fix parameter names with {{baseName}}

[ePaul]

PR checklist

• Read the contribution guidelines.
• Ran the shell/batch script under ./bin/ to update Petstore sample so that CIs can verify the change.
  → bin/groovy-petstore.sh
• Filed the PR against the correct branch: master for non-breaking changes

Description of the PR

This fixes (or hopes to fix) part of #4898 for the groovy generator.

The problem likely occurred when a query or header parameter name (as declared in the OpenAPI definition) is of a form which doesn't match the form used in Groovy, or is a reserved word there. In this case the parameter gets renamed for use in the code, and the parameter will be sent with the sanitized name instead of the original one.

This commit changes the replacement to using {{baseName}} (which is the original name of the parameter definition as parsed from the API definition) instead of {{paramName}} (which is the sanitized version of the parameter name).

Note that it looks like the Groovy generator has no support at all for path, form or body parameters – those are accepted by the generated code, but then ignored, and not passed to the server. I didn't try to fix this, as my Groovy knowledge is too rusty for this, but added some TODOs in the template. Related issue: #4289

Our Petstore sample API definition doesn't seem to contain any query parameter which would get modified by the sanitation, so the regenerated samples just have a single difference in a header parameter (which looks better now to me).

I don't know anything about Groovy, so this needs review by Groovy experts.

[wing328]

@ePaul the fix looks good to me. I should be able to add the path parameter support.