Validate some fields on the ES index settings

Maybe we want to restrict some fields on the settings like number of shards or replicas to allow. We could have those fields ranges being validated against some configuration parameters.

Although this might not be very important since views writes is already guarded by ACLs.

Start by locating the Elasticsearch index-settings handling and the configuration parameters that could define allowed ranges. Determine which shard and replica fields require validation and how ACL-protected view writes interact with that decision. Done means the intended constraints are defined and consistently enforced, with coverage for accepted and rejected settings.

Written by the indexing model from the issue text.