Bug: case sensitive handling of HTTP Header

[AndreasBergmeier6176]

What version of ogen are you using?

$ go list -m github.com/ogen-go/ogen

github.com/ogen-go/ogen v1.3.0

Can this issue be reproduced with the latest version?

Yes

What did you do?

Generate bindings. As a result the following was generated:

	if _, ok := r.Header["Content-Type"]; !ok && r.ContentLength == 0 {
		return req, close, nil
	}
	ct, _, err := mime.ParseMediaType(r.Header.Get("Content-Type"))
	if err != nil {
		return req, close, errors.Wrap(err, "parse media type")
	}

What did you expect to see?

Would expect r.Headers to only be accessed via Get due to case insensitivity.

What did you see instead?

Direct access of r.Header["Content-Type"] which does not handle insensitivity.

[ghost]

Incoming headers are canonicalized by Go http server, not sure if it is really a problem.

[AndreasBergmeier6176]

Are you sure this cannot be a problem when writing tests against the API?