entc: abandon plugins

Summary:
Go plugin is not a good solution for both internal and external usage.
It's hard to manage and maintain matching versions (both Go and external libraries), and it does not support Windows.

Reviewed By: alexsn

Differential Revision: D16582217

fbshipit-source-id: 81876d2c6f30bbfc16ecf9e5000f0670f2e62484

entc/load/testdata/valid/schema.go

@@ -0,0 +1,41 @@
+package valid
+
+import (
+	"fbc/ent"
+	"fbc/ent/field"
+)
+
+// User holds the user schema.
+type User struct {
+	ent.Schema
+}
+
+func (User) Fields() []ent.Field {
+	return []ent.Field{
+		field.Int("age"),
+		field.String("name"),
+	}
+}
+
+// Group holds the group schema.
+type Group struct {
+	ent.Schema
+}
+
+func (Group) Fields() []ent.Field {
+	return []ent.Field{
+		field.Time("expired_at"),
+		field.String("organization"),
+	}
+}
+
+// Tag holds the tag schema.
+type Tag struct {
+	ent.Schema
+}
+
+func (Tag) Fields() []ent.Field {
+	return []ent.Field{
+		field.String("text"),
+	}
+}