[REQ][typescript] Enable header override at request time

[davidgamero]

Is your feature request related to a problem? Please describe.

When making requests, the current options only allow passing in a full Configuration, but for cases like supplying a Content-Type for a JSON Merges it would be much easier to allow passing an additional header when making a request

Describe the solution you'd like

Adding an additional input, or overloading the optional _options?: Configuration parameter for generated operations

Alternatively, allow supplying custom middleware at request time, which would provide a more potentially more flexible solution, and allow the existing middleware implementation to handle the header override

Describe alternatives you've considered

The current approach has been to re-created a fully new Configuration from an existing one each time we want to change a header, and then supply the header addition as a middleware.
We could continue to modify the entire configuration per-request, continuing to rely on internals instead of using a dedicated per-request mechanism

Additional context

Thread from kubernetes-client/javascript discussion: kubernetes-client/javascript#754 (comment)