Support configuring replica region and endpoint

[MatheusRich]

I'm trying to setup replication using Hetzner's Object Storage, but the default S3 options won't work.

LMK if there's another way around this and if this isn't necessary.

[adrienpoly]

I ran into a similar issue with R2 where (unless mistaken) I needed to provide the endpoint

as a temporary solution I assign the env variable in the initializer

ENV["LITESTREAM_REPLICA_ENDPOINT"] = litestream_credentials&.replica_endpoint

and use it in litestream.yml

- path: storage/staging_rubyvideo.sqlite3
    replicas:
      - type: s3
        endpoint: $LITESTREAM_REPLICA_ENDPOINT
        bucket: $LITESTREAM_REPLICA_BUCKET
        path: storage/staging_rubyvideo.sqlite3
        access-key-id: $LITESTREAM_REPLICA_ACCESS_KEY_ID
        secret-access-key: $LITESTREAM_REPLICA_SECRET_ACCESS_KEY