entc/load: enable adding additional fields to the generated entities

Summary: In some cases (like xwf auth service), you want to add additional fields to the generated model.

Reviewed By: alexsn

Differential Revision: D17223674

fbshipit-source-id: fb4be71b388c6bd107e6bac242133c237fe25599

entc/load/testdata/valid/schema.go

@@ -5,6 +5,9 @@
 package valid
 
 import (
+	"log"
+	"sync"
+
 	"github.com/facebookincubator/ent"
 	"github.com/facebookincubator/ent/schema/field"
 )
@@ -12,6 +15,13 @@ import (
 // User holds the user schema.
 type User struct {
 	ent.Schema
+
+	// add additional struct-only
+	// fields to the generated model.
+	Tenant string      `json:"tenant,omitempty"`
+	Logger *log.Logger // Comment.
+	sync.Mutex
+	Ignored ent.Interface // Ignored comment.
 }
 
 func (User) Fields() []ent.Field {