Slack Auth fix: replace passport-slack implementation

[ehossack]

This commit replaces the observably defunct @aoberoi/passport-slack
implementation with that of nmaves's passport-slack-oauth2

I have (manually) tested this on a local installation to verify it does correctly work with a slack + wiki.js installation.

[ehossack]

This addresses #3335

[ehossack]

Looking at the releases, it looks like 3.0 is the next targeted release. Given that the 2.X stream is currently broken for slack auth, and assuming we're able to create a fix within this PR, is it viable to consider cutting a 2.X release before the 3.0 beta?
(selfish question of course, but I'm not sure the viability of running a patched version myself - given the giant red "THIS IS A DEV VERSION" warning that happens with node serve 😅)

[nasiralamreeki]

release

The 3.0 repo doesn't even look very active so my guess is a beta isn't coming anytime soon. Would be nice to see more updates to 2.x until there is a beta as 2.x still has bugs.

[omenos]

Thanks for doing this @ehossack! Hopefully this gets merged and a new 2.x cut, would be really helpful for a project I'm working on.

You might be able to generate the non-dev banner build by following the steps in the dev/build/Dockerfile file.

Edit: Need to change the dev and version vars in package.json.