Added exception to editCurrency method in Currency

Declared `throws IllegalArgumentException` for `editCurrency` to handle duplicate currency names explicitly. This improves API safety and clarity for consumers.

Author: NonSwag

src/main/java/net/thenextlvl/service/api/economy/currency/Currency.java

@@ -111,8 +111,9 @@ default Component format(Number amount, Audience audience) {
      *
      * @param consumer a {@code Consumer} that accepts a {@code Builder} instance to define customizations for the currency
      * @return {@code true} if the edit succeeded, otherwise {@code false}
+     * @throws IllegalArgumentException if a currency with the same name already exists
      */
-    boolean editCurrency(Consumer<Builder> consumer);
+    boolean editCurrency(Consumer<Builder> consumer) throws IllegalArgumentException;
 
     /**
      * A builder interface for constructing instances of {@link Currency}.