[F] Fix one-to-one relationship in email confirmation

src/main/java/icu/samnyan/aqua/net/db/AquaEmailConfirmation.kt

@@ -21,7 +21,7 @@ class EmailConfirmation(
     var createdAt: Instant = Instant.now(),
 
     // Linking to the AquaNetUser
-    @OneToOne
+    @ManyToOne
     @JoinColumn(name = "auId", referencedColumnName = "auId")
     var aquaNetUser: AquaNetUser = AquaNetUser()
 ) : Serializable
@@ -29,4 +29,5 @@ class EmailConfirmation(
 @Repository
 interface EmailConfirmationRepo : JpaRepository<EmailConfirmation, Long> {
     fun findByToken(token: String): EmailConfirmation?
+    fun findByAquaNetUserAuId(auId: Long): List<EmailConfirmation>
 }

src/main/resources/db/migration/mariadb/V251_2__add_aquanet_user.sql

@@ -42,8 +42,5 @@ CREATE TABLE aqua_net_email_confirmation
     CONSTRAINT pk_email_confirmation PRIMARY KEY (id)
 );
 
-ALTER TABLE aqua_net_email_confirmation
-    ADD CONSTRAINT uc_email_confirmation_aqua_user UNIQUE (au_id);
-
 ALTER TABLE aqua_net_email_confirmation
     ADD CONSTRAINT FK_EMAIL_CONFIRMATION_ON_AQUA_USER FOREIGN KEY (au_id) REFERENCES aqua_net_user (au_id);