Validate data against expected coverage

[stefanb]

Is your feature request related to a problem? Please describe.
When a source changes unexpectedly, or there is a bug in the source definition / conform (eg when writing / adjusting the source json), or there is a bug in the processing pipeline (eg #90, openaddresses/openaddresses#5917) it goes unnoticed until someone looks at it (the rendered map with the data or the data itself).

Describe the solution you'd like
Validate that the sourced data roughly fits into the defined / expected coverage, at least into the required country. Some tolerance should be allowed for rough border cases. This could be implemented using a tolerance buffer zone (few km) or just that more than 90% of data should be within the expected coverage country (or region, if defined in source).

Describe alternatives you've considered
Periodically manually checking the output (rendered map and/or data).

Additional context
This would help detecting wrong projections and lat/lon attribute mappings.