Improve documentation for kibana_user role assignment

[legrego]

Kibana version: >= 6.5

We have historically taught our users that they need to assign the kibana_user role to all users who wish to access Kibana. With the introduction of Spaces and other RBAC initiatives, this is no longer the case.

The kibana_user role is now a Kibana superuser role of sorts, because it allows read/write access to all spaces, and it also grants the ability to manage spaces themselves.

Administrators who wish to secure access to specific spaces should not be assigning the kibana_user role to their end users anymore, but instead create custom roles that are tailored to their needs.

[elasticmachine]

Pinging @elastic/kibana-security

[kobelb]

#26652 will help with this

[lcawl]

I think the description of the built-in kibana_user role in https://www.elastic.co/guide/en/elastic-stack-overview/master/built-in-roles.html is out-dated.
Likewise, it sounds like we no longer want to recommend assigning the kibana_user role in the "Getting started with security" tutorial: https://www.elastic.co/guide/en/elastic-stack-overview/master/get-started-roles.html

[kobelb]

I think the description of the built-in kibana_user role in https://www.elastic.co/guide/en/elastic-stack-overview/master/built-in-roles.html is out-dated.

Agreed, I thought we'd revised the terminology used here previously, but I must be mis-remembering.

Likewise, it sounds like we no longer want to recommend assigning the kibana_user role in the "Getting started with security" tutorial: https://www.elastic.co/guide/en/elastic-stack-overview/master/get-started-roles.html

For getting started, it's fine to use the kibana_user role; however, some phrasing should be changed. Would you like for me to create a PR to address these two docs issues, or would you prefer to do so?

#25722 provides a bit of context around our future direction for these two roles. Apologies for letting the stack docs get so out of date.

[lcawl]

Thanks for the information @kobelb ! If you are willing to create the PR, that's great. I'm happy to review or add suggestions. No worries about the delay--I just wanted to put a pin in them when I stumbled across them while making other updates.

[kobelb]

You got it! I'll get a PR together for this.

[gchaps]

@kobelb, @lcawl. Can we close this issue?