Log failures returned by the Elasticsearch API

[SPMaibornwolff]

Elcep should log the failures which are returned by the Elasticsearch API.
I.e. a request with a missing configuration for text field aggregation does not fail. Instead it returns a document with failures:
{ "took": 1, "timed_out": false, "_shards": { "total": 2, "successful": 3, "skipped": 4, "failed": 4, "failures": [ { "shard": 0, "index": "index", "node": "node", "reason": { "type": "illegal_argument_exception", "reason": "Fielddata is disabled on text fields by default. Set fielddata=true on [text_field_name] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory. Alternatively use a keyword field instead." } } ] }, ... }
Such failures should be logged.