chore: Formatting fixes

src/main/java/eu/ztsh/wymiana/exception/ExchangeFailedException.java

@@ -1,6 +1,6 @@
 package eu.ztsh.wymiana.exception;
 
-public class ExchangeFailedException extends RuntimeException{
+public class ExchangeFailedException extends RuntimeException {
 
     public ExchangeFailedException() {
         this("An exchange error has occurred");

src/main/java/eu/ztsh/wymiana/service/CurrencyService.java

@@ -53,7 +53,7 @@ public class CurrencyService {
     }
 
     private Currency create(String symbol) {
-        // TODO: check if supported
+        // TODO: check if supported - now limited to PLN <-> USD
         return new Currency(symbol.toUpperCase(), 0D);
     }