[+] Backend card linking

src/main/java/icu/samnyan/aqua/sega/general/service/CardService.kt

@@ -33,10 +33,17 @@ class CardService(val cardRepo: CardRepository)
 
     /**
      * Find a card by its access code
+     *
+     * If the card is linked to a user, return the user's ghost card instead
+     *
      * @param accessCode String represent of an access code
      * @return Optional of a Card
      */
-    fun getCardByAccessCode(accessCode: String?): Optional<Card> = cardRepo.findByLuid(accessCode)
+    fun getCardByAccessCode(accessCode: String?): Optional<Card> = Optional.ofNullable(
+        cardRepo.findByLuid(accessCode).getOrNull()?.let {
+            it.aquaUser?.ghostCard ?: it
+        }
+    )
 
     /**
      * Register a new card with access code