GOAL: Document a deployment plan for the maps internationalization feature that we can confidently execute **without causing any downtime** and that **supports rollback** if anything goes wrong.
Proposed plan:
# [x] 1. Introduce 'kartotherian_storage_id' and 'tilerator_storage_id' hiera variables with the current value of 'storage_id' (v3) and use them for their respective services.
# [x] 2. Deploy tilerator@i18n (it is using keyspace `v4`)
# Regenerate all tiles. In the meantime, kartotherian is serving tiles from keyspace `vN`, they may be getting a bit stale but that's ok
# Deploy kartotherian with i18n code with existing sources serving tiles from keyspace `vN` and new sources serving from `vN+1`
# To do official release, clean up sources to have only on set serving from keyspace `vN+1`
# Invalidate varnish cache
# Eventually drop keyspace `vN` to save space
# Set a single 'storage_id' variable that contains `vN+1` and is used by both tilerator and kartotherian
Alternate ending (after: Deploy kartotherian@i18n):
# Redeploy kartotherian (non-i18n) and serve tiles from keyspace `vN`
# Redeploy tilerator (non-i18n) and find a way to re-process old osm updates
All questions/comment/simplifications/warnings/etc are welcome.