[BE] feat: Festival, Ticket 테이블의 school_id의 not null 제약조건 추가(#468) (#469

)

* refactor: Ticket,Festival 도메인 School notnull 제약사항 추가

* feat: flyway sql 추가

backend/src/main/java/com/festago/festival/domain/Festival.java

@@ -41,6 +41,7 @@ public class Festival extends BaseTimeEntity {
     @Size(max = 255)
     private String thumbnail;
 
+    @NotNull
     @ManyToOne(fetch = FetchType.LAZY)
     private School school;
 

backend/src/main/java/com/festago/ticket/domain/Ticket.java

@@ -42,6 +42,7 @@ public class Ticket extends BaseTimeEntity {
     @ManyToOne(fetch = FetchType.LAZY)
     private Stage stage;
 
+    @NotNull
     private Long schoolId;
 
     @NotNull

backend/src/main/resources/db/migration/V6__school_notnull.sql

@@ -0,0 +1,5 @@
+alter table festival
+    modify school_id bigint not null;
+
+alter table ticket
+    modify school_id bigint not null;