Change Details

Implement a SiteLookup service based on JSON files, as proposed by {T113034}. The JSON structure should allow for all features we have in Site and in Interwiki. In addition, the concept of site groups should be extended to allow a single site to be in multiple groups. When ingesting the JSON files, data from different files is deep-merged. For some fields, separate lookup arrays (indexes) are maintained: lookup by global id, group, by interwiki prefix, etc.