testing: was added test data without pointer type

tests/testdata/src/relations_check/negative.go

@@ -1,5 +1,7 @@
 package relations_check
 
+// Many-to-many
+
 type Library struct {
 	Id    uint    `gorm:"primaryKey"`
 	Books []*Book `gorm:"many2many:library_book;"`
@@ -14,3 +16,13 @@ type Employee struct {
 	Id           uint        `gorm:"primaryKey"`
 	Subordinates []*Employee `gorm:"many2many:employee_subordinates;"` // self-reference
 }
+
+type Publisher struct {
+	Id      uint      `gorm:"primaryKey"`
+	Writers []*Writer `gorm:"many2many:publisher_books;"`
+}
+
+type Writer struct {
+	Id         uint        `gorm:"primaryKey"`
+	Publishers []Publisher `gorm:"many2many:publisher_books;"`
+}