Treat ListSharee as access table

This is so that multiple users can be paired with a single list.

In the future, we may want to reconsider list deletion behavior to simply remove a user's access and only delete it when no one has access.

We may also want the user deletion Lambda to use the list deletion Lambda when it is created.

Lambdas/Lists/ListShare/src/ListSharePOST.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 ListSharePOST implements RequestHandler<Map<String,Object>, Object> {
+
+    public Object handleRequest(Map<String, Object> inputMap, Context unfilled) {
+        return BasicHandler.handleRequest(inputMap, unfilled, ListSharer.class);
+    }
+}