Multipart request bodies are missing encoding information

Throughout the API surface, there are multiple operations that accept a multiple request body.
The description is missing encoding information for the parts, see the example overlay action below.
This lack of information hinders code generation ability to enable proper representation of the payload, and serialization abilities.

- update:
      encoding:
        file:
          contentType: application/octet-stream
        model:
          contentType: text/plain
        chunking_strategy:
          contentType: text/plain
        include:
          contentType: application/json
        language:
          contentType: text/plain
        prompt:
          contentType: text/plain
        response_format:
          contentType: text/plain
        stream:
          contentType: application/json
        temperature:
          contentType: application/json
        timestamp_granularities:
          contentType: application/json
    description: Adds missing parameters for the path item
    target: >-
      $.paths['/audio/transcriptions'].post.requestBody.content['multipart/form-data']

Start by reviewing the OpenAPI request-body definitions for multipart operations and compare them with the example target at /audio/transcriptions POST. Identify each part that lacks encoding information, then update the affected descriptions so their content types are represented consistently. Done means the multipart request bodies expose encoding metadata needed for payload representation and serialization.