Add: Exception to throw when required Parameter is not found

src/main/java/ch/unibas/dmi/dbis/cs108/casono/server/network/parser/MissingParameterException.java

@@ -0,0 +1,14 @@
+package ch.unibas.dmi.dbis.cs108.casono.server.network.parser;
+
+public class MissingParameterException extends RuntimeException {
+    private final String parameterKey;
+
+    public MissingParameterException(String message, String parameterKey) {
+        super(message);
+        this.parameterKey = parameterKey;
+    }
+
+    public String getParameterKey() {
+        return parameterKey;
+    }
+}