[Feature] New feature to use middlewares in go-swagger more flexible.

[Icarus9913]

In the current go-swagger version, we have to modify 'configure_xxx.go' file and hard code to register the middleware with function setupMiddlewares or setupGlobalMiddleware. Although it won't get overridden with subsequent generations.

With @casualjim said:
The main thing for this being inert is that it's been like this from the start, and introducing a change that can break codebases is something I want to avoid because we have so many consumers

Maybe there should be one Default config make keep the current private function. And we could add something like a global variable for outer users to modify and register middlewares , in which situation we regard the generated server codes as SDK and would not ever to modify it.