Auth Drawer: Use redux store to load settings

[linoman]

What is this feature?

Improves code by using existing actions to fetch and retrieve settings information.

Why do we need this feature?

The original implementation used the backend service to update the backend settings. While this works, it could be improved.

Who is this feature for?

IAM

Which issue(s) does this PR fix?:

Fixes #

Special notes for your reviewer:

Please check that:

• It works as expected from a user's perspective.
• If this is a pre-GA feature, it is behind a feature toggle.
• The docs are updated, and if this is a notable improvement, it's added to our What's New doc.

[alexanderzobnin]

I would recommend using async/await approach, it produces much clearer code.

try {
  await saveSettings()
  await loadSettings(false)
  notifyApp.success('Settings saved')
} catch (error) {
  notifyApp.error('Failed to save settings')
}

You also could put loadSettings() call into saveSettings() action if you always call it after (I think you in most of cases need to re-fetch settings after saving it to display updated values).

[linoman]

I prefer promises over async calls, but this is just me. I have changed the code as per your suggestion.

[linoman]

I decided not to include loadSettings inside saveSettings because I'm aware they're being used by the old LDAP and SAML UI. I rather keep this clean for now.

Do you think is necessary?

[grafana-delivery-bot]

Hello @linoman!
Backport pull requests need to be either:

• Pull requests which address bugs,
• Urgent fixes which need product approval, in order to get merged,
• Docs changes.

Please, if the current pull request addresses a bug fix, label it with the type/bug label.
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