# 벤더 설정 — 사건을 기록한 javadoc
  /**
   * The vendor's migration location, as a default rather than as an override.
   *
   * <p>This unconditionally called {@code locations(...)}, which replaces whatever Spring bound
   * from {@code spring.flyway.locations}. An operator could therefore set {@code
   * SPRING_FLYWAY_LOCATIONS} to add the capability streams, watch Flyway report a successful
   * migration, and get only the vendor stream — the property was read, bound, and then discarded by
   * a customizer that runs after it. The {@code local-notification-ingest} lane set seven locations
   * and applied one.
   *
   * <p>It is the same shape as {@code application-local.yml}'s literal pins, which outranked every
   * environment a caller supplied, and the same fix: contribute the value when nobody has chosen
   * one, and stay out of the way when somebody has. A deployment that names its own locations is
   * responsible for including this one, which is exactly the responsibility it took by naming them.
   *
   * @param environment the resolved environment, consulted for an operator-supplied value
   * @return the customizer
   */

# 벤더 설정 — 지금 구현
  @Bean
  public static FlywayConfigurationCustomizer postgreSqlFlywayLocationCustomizer(
      org.springframework.core.env.Environment environment) {
    return configuration -> {
      String chosen = environment.getProperty("spring.flyway.locations", "").trim();
      if (chosen.isEmpty()) {
        configuration.locations("classpath:db/migration/postgresql");
      }
    };
  }

# 같은 빈 이름을 쓰는 sample 쪽 — 아직 무조건 호출
   * {@code static @Bean} (called without instantiating the owning class, so no
   * {@code @PersistenceContext} injection during Flyway init). Sets both migration locations:
   * production {@code db/migration/postgresql} + sample {@code db/sample-migration}. {@code
   * locations(...)} replaces rather than appends, so this — not {@code spring.flyway.locations} in
   * application.yml — is the effective source of truth. See README.
   */
  @Bean
  public static FlywayConfigurationCustomizer postgreSqlFlywayLocationCustomizer() {
    return configuration ->
        configuration.locations(
            "classpath:db/migration/postgresql", "classpath:db/sample-migration");
  }

# H2 쪽은 커스터마이저를 아예 두지 않는다
21: * <p><b>No Flyway location customizer, deliberately.</b> The PostgreSQL vendor points Flyway at