[BUG] [typescript-axios] Query parameters do not support `explode: true, style: form`

Created by: dantman

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

OpenAPI supports parameters defined with the following.

name: color
in: query
style: form
explode: true

https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.3.md#style-values

Parameters defined like this and given an array output query strings like color=blue&color=black&color=brown.

However currently a typescript-axios client made by openapi-generator would instead output color=blue%2Cblack%2Cbrown.

openapi-generator version

$ openapi-generator version
5.0.0-beta2

OpenAPI declaration file content or url

parameters:
- name: color
  in: query
  style: form
  explode: true
  schema:
    type: array
    item:
      type: array
        - in: query
          name: Balance.Currency
          style: form
          explode: true
          schema:
            type: string

Generation Details

openapi-generator generate -i openapi.yaml -g typescript-axios -c config.yaml

Suggest a fix

I think that apiInner.mustache needs to be updated to include handling for this type of collection format.

https://github.com/OpenAPITools/openapi-generator/blob/78611b3e387128b5f768865e4dfa8b4736ba571c/modules/openapi-generator/src/main/resources/typescript-axios/apiInner.mustache#L107-L138