Issue Summary

There are two similar threads that appeared on the community recently and they are both related to similar stuff. 

Once the user-A registers webhooks to the URL-A, then the user-B can't register webhooks to URL-B and they can't display the URL used by the user-A

This is reproducible on Data Center: no

Steps to Reproduce

1. Create a 3 LO app that allows users to register the webhooks
2. Install the app on the instance as USER-A
3. Register a webhook to URL-A
4. Install the app as USER-B

Expected Results

1. The limit should take the user under consideration - allow one recipient URL per pair app & user.
   OR
2. Get all webhooks should return all registered webhooks for that app

Actual Results

1. You can't register a webhook to URL-B as USER-B
2. You can't list webhooks registered by USER-A, so you can't check the URL used by USER-A

Workaround

Currently, there is no known workaround for this behavior. A workaround will be added here when available