sessionStorage.redis.sentinel.connectionUrls creates array, but expects string

[Schueni1]

connectionUrls is of wrong type. Should be a list, but expects string.

[tuunit]

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For example:

## Description
The `connectionUrls` attribute of `sessionStorage.redis.cluster` and `sessionStorage.redis.sentinel` seem to be of the wrong type.

## Expected

```yaml
sessionSotrage:
  redis:
    cluster:
      # List of Redis cluster connection URLs comma separated (e.g. `"redis://127.0.0.1:8000, redis://127.0.0.1:8001"`)
      connectionsUrls: ""
\```

[tuunit]

Fixed by #268