fix: user model consistency checks

migrations/20251005-drop_duplicate_emails.go

@@ -0,0 +1,33 @@
+package migrations
+
+import (
+	"github.com/muety/wakapi/config"
+	"gorm.io/gorm"
+)
+
+func init() {
+	const name = "20251005-drop_duplicate_emails"
+	f := migrationFunc{
+		name:       name,
+		background: false,
+		f: func(db *gorm.DB, cfg *config.Config) error {
+			if hasRun(name, db) {
+				return nil
+			}
+
+			const q = "with t1 as " +
+				"(select id, row_number() over(partition by email order by id) as row_num from users where email is not null) " +
+				"update users set email = null " +
+				"where users.id in (select id from t1 where row_num > 1)"
+
+			if err := db.Exec(q).Error; err != nil {
+				return err
+			}
+
+			setHasRun(name, db)
+			return nil
+		},
+	}
+
+	registerPostMigration(f)
+}