Add support for Function and Trigger domain objects (#1060)

Vast commit, includes:

 * Introduces the Trigger domain entity.
 * Introduces the Fns domain entity.
 * V2 of the API for interacting with the new entities in swaggerv2.yml
 * Adds v2 end points for Apps to support PUT updates.
 * Rewrites the datastore level tests into a new pattern.
 * V2 routes use entity ID over name as the path parameter.

api/server/apps_v1_update.go

@@ -0,0 +1,47 @@
+package server
+
+import (
+	"net/http"
+
+	"github.com/fnproject/fn/api"
+	"github.com/fnproject/fn/api/models"
+	"github.com/gin-gonic/gin"
+)
+
+// TODO: Deprecate with V1 API
+func (s *Server) handleV1AppUpdate(c *gin.Context) {
+	ctx := c.Request.Context()
+
+	wapp := models.AppWrapper{}
+
+	err := c.BindJSON(&wapp)
+	if err != nil {
+		if models.IsAPIError(err) {
+			handleV1ErrorResponse(c, err)
+		} else {
+			handleV1ErrorResponse(c, models.ErrInvalidJSON)
+		}
+		return
+	}
+
+	if wapp.App == nil {
+		handleV1ErrorResponse(c, models.ErrAppsMissingNew)
+		return
+	}
+
+	if wapp.App.Name != "" {
+		handleV1ErrorResponse(c, models.ErrAppsNameImmutable)
+		return
+	}
+
+	wapp.App.Name = c.MustGet(api.AppName).(string)
+	wapp.App.ID = c.MustGet(api.AppID).(string)
+
+	app, err := s.datastore.UpdateApp(ctx, wapp.App)
+	if err != nil {
+		handleV1ErrorResponse(c, err)
+		return
+	}
+
+	c.JSON(http.StatusOK, appResponse{"AppName successfully updated", app})
+}