feat(web): add setting for minimum face count for face detection (#4128)

* feat: add setting for minimum face count for face detection

Adds the minimum face count setting to the web interface to
circumvent detection of strangers and random background people
if desired.

* fix: codestyle, remove max for face count

mobile/openapi/test/recognition_config_test.dart

@@ -26,6 +26,11 @@ void main() {
       // TODO
     });
 
+    // int minFaces
+    test('to test the property `minFaces`', () async {
+      // TODO
+    });
+
     // int minScore
     test('to test the property `minScore`', () async {
       // TODO