Auth: Azure AD OAuth (#20030)

* Implement Azure AD oauth

* Use go-jose and cleanup

* Update go-jose in go.mod

* cleanup

* Add unit tests

* Fix scopes

* Add documentation page

* Improve documentation

* Convert extract_role into function.

* Do not use upn and replace unique_name with preferred_username

* Configure login button

* Use official microsoft icon and color from branding guideline.

* Add Azure AD config section in sample.ini.

pkg/api/user.go

@@ -341,6 +341,8 @@ func GetAuthProviderLabel(authModule string) string {
 		return "GitHub"
 	case "oauth_google":
 		return "Google"
+	case "oauth_azuread":
+		return "AzureAD"
 	case "oauth_gitlab":
 		return "GitLab"
 	case "oauth_grafana_com", "oauth_grafananet":