SAML: Support auto login (#61685)

* SAML: Support auto login

* Add individual auto_login option for each OAuth provider

* Docs: Describe new auto_login option

* Minor refactor

pkg/setting/setting.go

@@ -1408,7 +1408,13 @@ func readAuthSettings(iniFile *ini.File, cfg *Cfg) (err error) {
 
 	DisableLoginForm = auth.Key("disable_login_form").MustBool(false)
 	DisableSignoutMenu = auth.Key("disable_signout_menu").MustBool(false)
+
+	// Deprecated
 	OAuthAutoLogin = auth.Key("oauth_auto_login").MustBool(false)
+	if OAuthAutoLogin {
+		cfg.Logger.Warn("[Deprecated] The oauth_auto_login configuration setting is deprecated. Please use auto_login inside auth provider section instead.")
+	}
+
 	cfg.OAuthCookieMaxAge = auth.Key("oauth_state_cookie_max_age").MustInt(600)
 	SignoutRedirectUrl = valueAsString(auth, "signout_redirect_url", "")
 	cfg.OAuthSkipOrgRoleUpdateSync = auth.Key("oauth_skip_org_role_update_sync").MustBool(false)