Remove the Redis databroker backend. According to
https://www.pomerium.com/docs/internals/data-storage#redis it has been
discouraged since Pomerium v0.18.
Update the config options validation to return an error if "redis" is
set as the databroker storage backend type.
* wip
* storage: add filtering to SyncLatest
* don't increment the record version, so intermediate changes are requested
* databroker: add support for query filtering
* fill server and record version
* postgres: databroker storage backend
* wip
* serialize puts
* add test
* skip tests for macos
* add test
* return error from protojson
* set data
* exclude postgres from cover tests
