Fix url parameter of find endpoint not being extracted properly

[TimJentzsch]

Relevant issue: N/A

Description:

While the /find/ endpoint was finally visible, it always returned an error response. Turns out that the url query parameter wasn't extracted properly so the value was always None.

I more or less tested it on the local setup so it should actually work now (hopefully).

Additionally, this fixes some types and makes the url parameter required.

Checklist:

• [x] Code Quality
• [x] Pep-8
• [ ] Tests (if applicable)
• [x] Success Criteria Met
• [x] Inline Documentation
• [ ] Wiki Documentation (if applicable)