Added add() methods for list properties

BankingClientModel/src/commonMain/kotlin/net/codinux/banking/client/model/BankAccount.kt

@@ -40,6 +40,18 @@ open class BankAccount(
     open val displayName: String
         get() = userSetDisplayName ?: productName ?: identifier
 
+    open fun addTransactions(transactions: List<out AccountTransaction>) {
+        (this.bookedTransactions as MutableList<AccountTransaction>).addAll(transactions)
+    }
+
+    open fun addPrebookedTransactions(transactions: List<out PrebookedAccountTransaction>) {
+        (this.prebookedTransactions as MutableList<PrebookedAccountTransaction>).addAll(transactions)
+    }
+
+    open fun addHoldings(holdings: List<out Holding>) {
+        (this.holdings as MutableList<Holding>).addAll(holdings)
+    }
+
     @get:JsonIgnore
     open val supportsTransactionRetrieval: Boolean
         get() = supportsAnyFeature(BankAccountFeatures.RetrieveBalance)