feat: improved e2e tests

frontend/app/cypress/BACKEND.md

@@ -0,0 +1,20 @@
+# Backend Mocking
+
+The backend _must_ be mocked using fixtures or other methods.
+
+You can use
+
+```typescript
+cy.interceptMultiSearch(...)
+cy.interceptSearch({extend: 'fixture', fixture: 'fixture', alias: 'alias'})
+cy.interceptGet({uid})
+```
+
+For mocking the responses based on a request.
+
+Paths in the commands will be relative to those, so
+`cy.interceptSearch({extend: 'request', fixture: 'response'})`
+will actually pull the fixtures from `request.search.req.json`
+and `response.search.res.json` respectively.
+
+If `fixture` is omitted, an empty response will be returned.