Specifying the utf-8 charset when exporting aggregate tables

[kobelb]

This resolves the issue of opening CSVs in most applications. However, Excel 2011 for Mac lacks UTF-8 support.

Closes #8637

[kobelb]

@epixa it's been requested by @LeeDr to backport this bugfix all the way back to v4.6.2. Is this appropriate for v5.0.0?

[epixa]

@kobelb @LeeDr I don't think this is appropriate for 5.0 or 4.6. It's not critical, and there is a workaround. I'd question whether we're even doing anything wrong at the moment, though I don't have any issue with us enhancing compatibility on our exported files, but that belongs in a minor release.

[LeeDr]

@epixa You're right in that there is a work-around. But I'd argue that its a very simple fix for a problem several people have reported and probably many more have hit but didn't report. There will be a significant number of users on Kibana 4.x for a long time.

[epixa]

@LeeDr Which can be said about most issues people encounter though, and many of those issues don't have any workaround. The only bug fixes that'll going into patch versions are critical ones.

And to be clear, I'm not convinced this is a bug at all. I'm all for improving this feature, but we're generating valid, strictly structured csv files. That Excel has a crappy default encoding setting for csv files isn't our fault, and this feature isn't an "export to Excel" feature.

The original issue was triaged as an enhancement, and I don't disagree with that assessment.

[jbudz]

LGTM