Upgrade to latest Graylog version

[nnoethling]

The latest graylog version is 6.1.5
Unfortunately this chart only supports 5.2.6 which was released in April last year.

Are there plans to upgrade it?
Is this chart still maintained?

[RogerSik]

Did someone successfully test an upgrade from 5 to 6 with modifying only the image.tag ?

[thiagoloureiro]

@RogerSik I just did, from 5 to 6.2.2
worked, no issues

[thiagoloureiro]

#170

[thiagoloureiro]

would be good also upgrade mongo + opensearch, they're quite outdated as well, @KongZ help us ;)

[thiagoloureiro]

done, we can close it. @nnoethling