[BUG][nodejs-express-server] HTTP headers with hyphens

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?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When the spec includes HTTP headers with hyphens (my-header), as is the standard, the generated service correctly converts the variable name to camelCase (myHeader), however at runtime, the requestParams object still uses the hyphen version (params['my-header']).

Therefore, the variable does not correctly map the value.

openapi-generator version

5.0.0-SNAPSHOT

OpenAPI declaration file content or url

        "parameters": [
          {
            "schema": {
              "type": "string"
            },
            "in": "header",
            "name": "my-header",
            "required": true
          }
        ]

Generation Details

docker run --rm -v ${PWD}:/local openapitools/openapi-generator-cli generate -i /local/api/api.json -t /local/core/swagger/mustache/nodejs-express-server/ -g nodejs-express-server -o /local/server/ --skip-validate-spec

Steps to reproduce

• Create an API specs with required HTTP headers, the header name must include a hyphen
• Generate a nodejs server
• Put a breakpoint in the generate Service, see that the variable is always undefined.

Suggest a fix

Whatever algorithm is used to transform the variable names, should be used when mapping the request params at run time.

Start with the nodejs-express-server template at core/swagger/mustache/nodejs-express-server/ and reproduce the issue using the Docker generation command in the report. Use an OpenAPI header named my-header, then inspect the generated Service and requestParams handling. Done means the runtime mapping uses the same camelCase variable name as the generated service.