NIFI-5317 - support non-ASCII X-Mailer header

[dtrodrigues]

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[ottobackwards]

This looks good, just two comments.

1. If we are going to add support for non-ascii, the test should test non-ascii, can we add that?
2. We now have a pattern of use in two places using with a try catch around setting headers with encoding, maybe we should have a function?

[dtrodrigues]

Header setting is now refactored into a function and there are tests for non-ascii headers

[ottobackwards]

We should include the header name in the message

[ottobackwards]

I don't see the non-ascii, am I missing something?

[dtrodrigues]

The test is for the non-ascii accented 'i' here in the first 'i' of "TestingNífi" on lines 140/167 as well as for the accented 'u' in "Búlk" https://github.com/apache/nifi/pull/2800/files/1325c094326eb0b89b4516a99c2065ef8b2d8009#diff-c1df47b56b59d9c7ef5e22043c7cd1a7R140

[dtrodrigues]

I updated the test X-Mailer header to be more explicit that it's non-ASCII

[ottobackwards]

Yikes, sorry.

[ottobackwards]

+1 LGTM, mvn install and contrib-check pass, use of MineType utility per best practices.

[pvillard31]

+1, merging to master, thanks @dtrodrigues @ottobackwards