Index on UID

**Problem**
For OSMContributionView each version of an entity has to be checked for the filters. For a global query this results in `mean nr of Versions (1.7) * entites` contributions being fed to the filter.

**Desired solution**
An index per GridCell (might be better then per OSH-Entity) possibly in form of a bitmap to exclude whole grid-cells based on a set of user-ids.

**Alternative**
?

**Additional context**
User-specific queries might get more common in future.