The ingest date processor is currently only able to parse joda formats.
However it is not using the existing elasticsearch classes but access
joda directly. This means that our existing BWC layer does not notify
the user about deprecated formats. This commit switches to use the
exising Elasticsearch Joda methods to acquire a date format, that
includes the BWC check and the ability to parse java 8 dates.
The date parsing in ingest has also another extra feature, that the
fallback year, when a date format without a year is used, is the current
year, and not 1970 like usual. This is currently not properly supported
in the DateFormatter class. As this is the only case for this feature
and java time can take care of this using the toZonedDateTime() method,
a workaround just for the joda time parser has been created, that can be
removed soon again from 7.0.
9e350d027e