NIFI-8175: Add WindowsEventLogReader controller service

[mattyb149]

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Description of PR

Adds a WindowsEventLogReader CS that assumes XML input (from ConsumeWindowsEventLog, ParseEvtx, etc.) and transforms it into NiFi Records. This can be used with any record-based processor.

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[exceptionfactory]

This looks like a straightforward implementation with helpful documentation and unit tests. See individual comments for a few questions and potential optimizations.

[exceptionfactory]

This could be replaced with the Apache Commons StringUtils.isNotBlank()

[mattyb149]

True but I am using the nifi utils version of StringUtils

[exceptionfactory]

Sounds good, thanks for the reply.

[exceptionfactory]

Is there a reason for using the src/test/resources path as opposed to using something like TestWindowsEventLogRecordReader.class.getResourceAsStream("/windowseventlog/single_event.xml")?

[mattyb149]

Only for consistency, the src/test/resources thing appears all over the NiFi codebase so it's what I'm used to

[exceptionfactory]

Thanks for the reply, that makes sense.

[exceptionfactory]

Thanks for making the updates @mattyb149, looks good! +1

[exceptionfactory]

Thanks for the PR @mattyb149, merging into main.