Fix datastore error for inexistent app (#493)

* fix datastore error inexistent app

* fix get route error handling

* fix API errors handling and tests

api/server/error_response.go

@@ -0,0 +1,35 @@
+package server
+
+import (
+	"context"
+	"errors"
+	"github.com/gin-gonic/gin"
+	"github.com/iron-io/functions/api/models"
+	"github.com/iron-io/runner/common"
+	"net/http"
+)
+
+var ErrInternalServerError = errors.New("Something unexpected happened on the server")
+
+func simpleError(err error) *models.Error {
+	return &models.Error{Error: &models.ErrorBody{Message: err.Error()}}
+}
+
+var errStatusCode = map[error]int{
+	models.ErrAppsNotFound:        http.StatusNotFound,
+	models.ErrAppsAlreadyExists:   http.StatusConflict,
+	models.ErrRoutesNotFound:      http.StatusNotFound,
+	models.ErrRoutesAlreadyExists: http.StatusConflict,
+}
+
+func handleErrorResponse(c *gin.Context, err error) {
+	ctx := c.MustGet("ctx").(context.Context)
+	log := common.Logger(ctx)
+	log.Error(err)
+
+	if code, ok := errStatusCode[err]; ok {
+		c.JSON(code, simpleError(err))
+	} else {
+		c.JSON(http.StatusInternalServerError, simpleError(err))
+	}
+}