Fluentd fails to send logs with unknown property

Issue

• Fluentd fills up with illegal argument exceptions due to "id" or other custom properties

2018-06-14 14:33:21 +0200 [debug]: Elasticsearch errors returned, retrying:  {"took"=>2, "errors"=>true, "items"=>[{"create"=>{"_index"=>"project.test-prod.286e429c-8efd-11e6-b4e5-0050569a3c52.2018.06.14", "_type"=>"com.redhat.viaq.common", "_id"=>"ZmU3YTE5NzYtMzIwZi00Njg1LTlmZTMtOTViN2Q1YjU4NzVi", "status"=>400, "error"=>{"type"=>"mapper_parsing_exception", "reason"=>"failed to parse [res.body]", "caused_by"=>{"type"=>"illegal_argument_exception", "reason"=>"unknown property [id]"}}}}, . . . "status"=>409, "error"=>{"type"=>"document_already_exists_exception", "reason"=>"[com.redhat.viaq.common][NTdhMGVhY2QtYTVmYy00MzQyLTk3YTQtZjJjMWU2YzQxYjBi]: document already exists", "shard"=>"0", . . .

2018-06-14 14:33:21 +0200 [warn]: temporarily failed to flush the buffer. next_retry=2018-06-14 14:38:21 +0200 error_class="Fluent::ElasticsearchErrorHandler::ElasticsearchError" error="Elasticsearch returned errors, retrying. Add '@log_level debug' to your config to see the full response" plugin_id="object:3ff3d4816f0c"
  2018-06-14 14:33:21 +0200 [warn]: suppressed same stacktrace