Create userID retrieval Lambda

Allow for the retrieval of userIDs from email (or just generally).

This may need the apigateway passthrough info modified for privacy protection

Lambdas/Lists/User/src/UserGET.java

@@ -0,0 +1,11 @@
+import com.amazonaws.services.lambda.runtime.Context;
+import com.amazonaws.services.lambda.runtime.RequestHandler;
+
+import java.util.Map;
+
+public class UserGET implements RequestHandler<Map<String,Object>, Object> {
+
+    public Object handleRequest(Map<String, Object> inputMap, Context unfilled) {
+        return BasicHandler.handleRequest(inputMap, unfilled, UserGetter.class);
+    }
+}