added REST API and simple unit test - and compose starter, still WIP for integ test

api/error.go

@@ -0,0 +1,50 @@
+package api
+
+import (
+	"github.com/go-chi/render"
+	"net/http"
+)
+
+//--------------------------------------------------------------------------
+// Error response payloads & renderers
+//--------------------------------------------------------------------------
+
+// ErrResponse renderer type for handling all sorts of errors.
+//
+// In the best case scenario, the excellent github.com/pkg/errors package
+// helps reveal information on the error, setting it on Err, and in the Render()
+// method, using it to set the application-specific error code in AppCode.
+type ErrResponse struct {
+	Err            error `json:"-"` // low-level runtime error
+	HTTPStatusCode int   `json:"-"` // http response status code
+
+	StatusText string `json:"status"`          // user-level status message
+	AppCode    int64  `json:"code,omitempty"`  // application-specific error code
+	ErrorText  string `json:"error,omitempty"` // application-level error message, for debugging
+}
+
+func (e *ErrResponse) Render(w http.ResponseWriter, r *http.Request) error {
+	render.Status(r, e.HTTPStatusCode)
+	return nil
+}
+
+func ErrInvalidRequest(err error) render.Renderer {
+	return &ErrResponse{
+		Err:            err,
+		HTTPStatusCode: 400,
+		StatusText:     "Invalid request.",
+		ErrorText:      err.Error(),
+	}
+}
+
+func ErrRender(err error) render.Renderer {
+	return &ErrResponse{
+		Err:            err,
+		HTTPStatusCode: 422,
+		StatusText:     "Error rendering response.",
+		ErrorText:      err.Error(),
+	}
+}
+
+var ErrNotFound = &ErrResponse{HTTPStatusCode: 404, StatusText: "Resource not found."}
+var ErrNotANumber = &ErrResponse{HTTPStatusCode: 400, StatusText: "Value not a number."}