Add OpenAPIServable interface

[dylanhitt]

per comment #337 (comment)

This interface is intended to unify the serving/configuration of OpenAPI endpoints between the fuego.Server and any adaptors. The current fuego.Server will need to be refactored to adhere to this interface. The current interface will look something like

type OpenAPIServable interface {
    Serve(openapi *fuego.OpenAPI)
}

The fuego.Server already has it's engine/server net/http Server wrapped. In order accomplish this in the case of adaptor. We will need to wrap our engine and say the gin.Engine into the same struct that adheres to this interface. The current code doing this for our server looks like this

// Registers the routes to serve the OpenAPI spec and Swagger UI.
func (s *Server) registerOpenAPIRoutes(jsonSpec []byte) {
	GetStd(s, s.OpenAPIServerConfig.SpecURL, func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		_, _ = w.Write(jsonSpec)
	})
	s.printOpenAPIMessage(fmt.Sprintf("JSON spec: %s%s", s.url(), s.OpenAPIServerConfig.SpecURL))

	if s.OpenAPIServerConfig.DisableSwaggerUI {
		return
	}
	Registers(s.Engine, netHttpRouteRegisterer[any, any]{
		s: s,
		route: Route[any, any]{
			BaseRoute: BaseRoute{
				Method: http.MethodGet,
				Path:   s.OpenAPIServerConfig.SwaggerURL + "/",
			},
		},
		controller: s.OpenAPIServerConfig.UIHandler(s.OpenAPIServerConfig.SpecURL),
	})
	s.printOpenAPIMessage(fmt.Sprintf("OpenAPI UI: %s%s/index.html", s.url(), s.OpenAPIServerConfig.SwaggerURL))
}

Methods used to print messages should try to adhere to the adaptors logging structure.

A side goal/side effect that may be possible is the removal of the OpenAPIServerConfig as I believe most of this would be able to get into the Engine.OpenAPIConfig