Add sample spec to catch external file reference issues in swagger-parser (#17773)

* add a sample that catches swagger-parser issues with external refs

* generate samples for new test spec

samples/client/echo_api/go-external-refs/response.go

@@ -0,0 +1,48 @@
+/*
+Echo Server API
+
+Echo Server API
+
+API version: 0.1.0
+Contact: team@openapitools.org
+*/
+
+// Code generated by OpenAPI Generator (https://openapi-generator.tech); DO NOT EDIT.
+
+package openapi
+
+import (
+	"net/http"
+)
+
+// APIResponse stores the API response returned by the server.
+type APIResponse struct {
+	*http.Response `json:"-"`
+	Message        string `json:"message,omitempty"`
+	// Operation is the name of the OpenAPI operation.
+	Operation string `json:"operation,omitempty"`
+	// RequestURL is the request URL. This value is always available, even if the
+	// embedded *http.Response is nil.
+	RequestURL string `json:"url,omitempty"`
+	// Method is the HTTP method used for the request.  This value is always
+	// available, even if the embedded *http.Response is nil.
+	Method string `json:"method,omitempty"`
+	// Payload holds the contents of the response body (which may be nil or empty).
+	// This is provided here as the raw response.Body() reader will have already
+	// been drained.
+	Payload []byte `json:"-"`
+}
+
+// NewAPIResponse returns a new APIResponse object.
+func NewAPIResponse(r *http.Response) *APIResponse {
+
+	response := &APIResponse{Response: r}
+	return response
+}
+
+// NewAPIResponseWithError returns a new APIResponse object with the provided error message.
+func NewAPIResponseWithError(errorMessage string) *APIResponse {
+
+	response := &APIResponse{Message: errorMessage}
+	return response
+}