fix: getServletContextName() must not throw UnsupportedOperationException (#448)

Author: deki

aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsServletContext.java

@@ -310,8 +310,7 @@ public void removeAttribute(String s) {
 
     @Override
     public String getServletContextName() {
-        // TODO: This can also come from a reader interface
-        throw new UnsupportedOperationException();
+        return null;
     }