[hotfix] Kakao 사용자 기존 이메일이 Null인 데이터에 대한 마이그레이션 이슈 해결 (#352)

Author: LeeMinwoo115

backend/src/main/java/com/back/domain/user/entity/User.java

@@ -47,7 +47,7 @@ public class User extends BaseEntity {
 	)
 	private Long id;
 
-	@Column(nullable = false, length = 100, unique = true)
+	@Column(length = 100)
 	private String email;
 
 	@Column(nullable = false, name = "full_name", length = 30)

backend/src/main/resources/db/migration/V20260110_01__set_not_null_and_unique_in_users_email.sql

@@ -1,5 +1,3 @@
-CREATE UNIQUE INDEX IF NOT EXISTS ux_users_email
-    ON users (email);
-
-ALTER TABLE users
-    ALTER COLUMN email SET NOT NULL;
+CREATE UNIQUE INDEX IF NOT EXISTS ux_users_email_not_null
+    ON users (email)
+    WHERE email IS NOT NULL;