entc/gen: add support for WithNamed<E> feature-flag (#2792)

* entc/gen: struct fields and methods for NamedEdge api

* entc/gen: generate WithNamedEdge methods for named-edges

* entc/gen: implement eager-loading for named-edges

* entc/gen: simplify eager-loading template

* entc/gen: drop support for unqiue edges in named-based loading

* all: codegen

* doc/website: named-edges feature-flag

* Update doc/md/eager-load.mdx

* Update doc/md/eager-load.mdx

examples/start/ent/car.go

@@ -45,8 +45,7 @@ type CarEdges struct {
 func (e CarEdges) OwnerOrErr() (*User, error) {
 	if e.loadedTypes[0] {
 		if e.Owner == nil {
-			// The edge owner was loaded in eager-loading,
-			// but was not found.
+			// Edge was loaded but was not found.
 			return nil, &NotFoundError{label: user.Label}
 		}
 		return e.Owner, nil

examples/start/ent/car_query.go

@@ -28,9 +28,8 @@ type CarQuery struct {
 	order      []OrderFunc
 	fields     []string
 	predicates []predicate.Car
-	// eager-loading edges.
-	withOwner *UserQuery
-	withFKs   bool
+	withOwner  *UserQuery
+	withFKs    bool
 	// intermediate query (i.e. traversal path).
 	sql  *sql.Selector
 	path func(context.Context) (*sql.Selector, error)

examples/start/ent/group_query.go

@@ -29,8 +29,7 @@ type GroupQuery struct {
 	order      []OrderFunc
 	fields     []string
 	predicates []predicate.Group
-	// eager-loading edges.
-	withUsers *UserQuery
+	withUsers  *UserQuery
 	// intermediate query (i.e. traversal path).
 	sql  *sql.Selector
 	path func(context.Context) (*sql.Selector, error)

examples/start/ent/user_query.go

@@ -30,7 +30,6 @@ type UserQuery struct {
 	order      []OrderFunc
 	fields     []string
 	predicates []predicate.User
-	// eager-loading edges.
 	withCars   *CarQuery
 	withGroups *GroupQuery
 	// intermediate query (i.e. traversal path).