[Dashboards]: Change to menu bars

[opensearch-trigger-bot]

Is your feature request related to a problem?
A new feature has been added.

What solution would you like?
Document the usage of the new feature.

What alternatives have you considered?
N/A

Do you have any additional context?
See please
opensearch-project/OpenSearch-Dashboards#1586.

[kavilla]

This feature will be released for 2.1

[hdhalter]

@kavilla - Is there any impact to documentation, other than a release note? Thanks.

[kavilla]

Hello @hdhalter,

I believe this page should reflect the updated config: https://opensearch.org/docs/latest/dashboards/branding/

[joshuarrrr]

@hdhalter The new branding config value added is opensearchDashboards.branding.useExpandedHeader, as seen in the new example config:

# opensearchDashboards.branding:
#   logo:
#     defaultUrl: ""
#     darkModeUrl: ""
#   mark:
#     defaultUrl: ""
#     darkModeUrl: ""
#   loadingLogo:
#     defaultUrl: ""
#     darkModeUrl: ""
#   faviconUrl: ""
#   applicationTitle: ""
#   useExpandedHeader: false

It currently defaults to true, which preserves the current behavior of 2 header bars, a top bar with the logo, and a bottom bar that now contains the rest of the existing menu items. (For a demo, see opensearch-project/OpenSearch-Dashboards#1583 (comment))

What users need to know about this new feature and setting:

1. The general behavior of the top navigation menu changed in v2.1: home button and loading icon changed, help and user management buttons moved (and any other navLinks registered by plugins)
2. Users who would like to opt-in to the new, condensed header experience can now do so by setting useExpandedHeader: false in their config file. (To help them choose, we should include screenshots of both modes).
3. In v3.0, the default behavior will change to useExpandedHeader: false, so any users that want to avoid switching to the new condensed can go ahead and explicitly set useExpandedHeader: true in their config now, or they can wait and do it when upgrading.
4. If users have custom plugins that add menu navLinks, and they'd like those links or buttons to remain on the top menu bar (instead of moving to the bottom bar), as in this example, they must make the following replacements:
   coreStart.chrome.navControls.registerRight(...) with coreStart.chrome.navControls.registerExpandedRight(...)
   and
   coreStart.chrome.navControls.registerCenter(...) with coreStart.chrome.navControls.registerExpandedCenter(...)
   (see [UX] Redesigned Global Header OpenSearch-Dashboards#1583 (comment) for complete steps)