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_delete.go

@@ -10,11 +10,11 @@ import (
 func (s *Server) handleAppDelete(c *gin.Context) {
 	ctx := c.Request.Context()
 
-	err := s.datastore.RemoveApp(ctx, c.MustGet(api.AppID).(string))
+	err := s.datastore.RemoveApp(ctx, c.Param(api.ParamAppID))
 	if err != nil {
 		handleErrorResponse(c, err)
 		return
 	}
 
-	c.JSON(http.StatusOK, gin.H{"message": "App deleted"})
+	c.String(http.StatusNoContent, "")
 }