[BUG][dart-dio-next] Generator uses url encoded contentType even if the server content type requires application/json

Created by: themisir

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?
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What's the actual output vs expected output?
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Description

I'm using Asp.Net Core Swashbuckle to generate openapi scheme for my backend. The backend supports multiple content-type variants of application/json. But generated code uses url encoded content type instead of application/json.

Here's generated code output which picks first match which is "application/json-patch+json".

contentType: [
  'application/json-patch+json',
  'application/json',
  'text/json',
  'application/_*+json',
].first

But then Did checks if content-type is application/json then uses json encoding but if it isn't, it uses url encoding and my server returns HTTP 415 Unsupported Media Type status.

openapi-generator version

5.1.0

OpenAPI declaration file content or url

The OpenAPI declaration that caused this issue was used for private api. So I couldn't share it here.

Generation Details

Steps to reproduce

Related issues/PRs

Suggest a fix

Overriding content-type header using command line options provided to generator CLI
Updating contentType matching part to choose most suitable match rather than first one