#23992 [BUG][PYTHON] Account for content-type parameters on request preparation

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Fixes #23990. A description and a guide on how to reproduce the issue can be found there.

The proposed changes include a new helper function called contenttype_matches that returns true when a given content-type string matches the given type and subtype, otherwise it returns false. Mime type parameters are ignored, but can be optionally be present in the provided string. It also allows for vendor specifications. For example, application/vendor+json is also considered valid against type=application, subtype=json.

@cbornet @tomplus @krjakbrjak @fa0311 @multani

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Summary by cubic

Fixes #23990 by making the Python client’s Content-Type matching robust during request prep. We now ignore parameters (including optional whitespace) and accept vendor-suffixed types so request bodies use the right encoder.

• Bug Fixes
  • Added contenttype_matches helper (case-insensitive, ignores MIME parameters/whitespace, supports vendor+subtype) and documented it at module scope.
  • Switched detection for JSON, application/x-www-form-urlencoded, multipart/form-data, and YAML (application/yaml, text/yaml, text/x-yaml) to use the helper.
  • Use content_type for text/* boolean handling; updated Python template and regenerated samples.