Testing Logstash filters

[babadofar]

It should be possible to test filters. This could be done by creating a test pipeline using the unmodified filters, and with custom input and input, for instance writing to and from files. A possible way to do this could be to separate the config into three folders, one for input, filter and output. Then the combinations of these folders could be configurable so as to be able to choose between test and prod pipelines.