util: add syspolicy package (#9550)

Add a more generalized package for getting policies.
Updates tailcale/corp#10967

Signed-off-by: Claire Wang <claire@tailscale.com>
Co-authored-by: Adrian Dewhurst <adrian@tailscale.com>

util/syspolicy/policy_keys.go

@@ -0,0 +1,35 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package syspolicy
+
+type Key string
+
+const (
+	// Keys with a string value
+	ControlURL Key = "LoginURL"  // default ""; if blank, ipn uses ipn.DefaultControlURL.
+	LogTarget  Key = "LogTarget" // default ""; if blank logging uses logtail.DefaultHost.
+
+	// Keys with a string value that specifies an option: "always", "never", "user-decides".
+	// The default is "user-decides" unless otherwise stated.
+	EnableIncomingConnections Key = "AllowIncomingConnections"
+	EnableServerMode          Key = "UnattendedMode"
+
+	// Keys with a string value that controls visibility: "show", "hide".
+	// The default is "show" unless otherwise stated.
+	AdminConsoleVisibility    Key = "AdminConsole"
+	NetworkDevicesVisibility  Key = "NetworkDevices"
+	TestMenuVisibility        Key = "TestMenu"
+	UpdateMenuVisibility      Key = "UpdateMenu"
+	RunExitNodeVisibility     Key = "RunExitNode"
+	PreferencesMenuVisibility Key = "PreferencesMenu"
+
+	// Keys with a string value formatted for use with time.ParseDuration().
+	KeyExpirationNoticeTime Key = "KeyExpirationNotice" // default 24 hours
+
+	// Boolean Keys that are only applicable on Windows. Booleans are stored in the registry as
+	// DWORD or QWORD (either is acceptable). 0 means false, and anything else means true.
+	// The default is 0 unless otherwise stated.
+	LogSCMInteractions      Key = "LogSCMInteractions"
+	FlushDNSOnSessionUnlock Key = "FlushDNSOnSessionUnlock"
+)