peek for Fermin

### This is not a PR
Just used to interchange info.
Will be removed after fulfilling its purpose
Additional comment: actually the filter for servicePath t is a little bit more complex, as it also have to take into account that a csub document without servicePath match every updateContext (it is implicitely "/#").

Inspired on how fillQueryServicePath() works for a similar case in the entities collection, I think the following should work (but it should be tested, anyway):

```
"servicePath": {$in: [ <regex as discussed in the previous comment>, null] }
```