Backend should not return 404 errors when no URLs are found

[halfwhole]

Describe the bug

When querying /api/user/url, if zero URLs match the query, the backend responds with a 404 error with body Urls not found. This should not be the response returned.

When the frontend tries to parse Urls not found as JSON, it results in an uncaught error:

This breaks the user page whenever the user makes queries that return 0 URLs.

Expected behaviour

Backend should return 200 with body {"urls":[],"count":0} - this is the behaviour in our latest release v1.69.0

On the frontend, when the user has no links, we should see this:

When the user has links and makes a query returning no results, we should see this:

Actual behaviour

Backend returns 404 error with body Urls not found - this is the current behaviour in develop

On the frontend, when the user has no links:

When the user has links and makes a query returning no results, the page simply does not update at all.

Additional thoughts

• Having backend integration tests could be useful in helping to catch regressions like these
• E2E tests should test for having no links or queries returning no results