Add option to make sign-in notification ongoing

Add an overlay boolean that allows setting the SIGN_IN notification as
an ongoing notification.

This can be useful to make sure users can always easily find the
notification to sign in to a captive portal, as studies have found that
some users have a tendency to dismiss notifications before reading them.
At the same time the notification shade is generally too crowded, which
is what causes such behaviors in the first place, so this option is not
enabled by default and should generally not be enabled without proper
user studies or metrics.

Bug: 173171709
Test: atest NetworkNotificationManagerTest
Change-Id: Ic187d2a2b7e49ad152ea2aa35bb784864b97473c
diff --git a/service/ServiceConnectivityResources/res/values/config.xml b/service/ServiceConnectivityResources/res/values/config.xml
index 9ff2a22..82d8e4f 100644
--- a/service/ServiceConnectivityResources/res/values/config.xml
+++ b/service/ServiceConnectivityResources/res/values/config.xml
@@ -123,4 +123,8 @@
     <string-array translatable="false" name="config_networkNotifySwitches">
     </string-array>
 
+    <!-- Whether to use an ongoing notification for signing in to captive portals, instead of a
+         notification that can be dismissed. -->
+    <bool name="config_ongoingSignInNotification">false</bool>
+
 </resources>
diff --git a/service/ServiceConnectivityResources/res/values/overlayable.xml b/service/ServiceConnectivityResources/res/values/overlayable.xml
index 717d08e..568deca 100644
--- a/service/ServiceConnectivityResources/res/values/overlayable.xml
+++ b/service/ServiceConnectivityResources/res/values/overlayable.xml
@@ -32,6 +32,7 @@
             <item type="integer" name="config_networkWakeupPacketMask"/>
             <item type="integer" name="config_networkNotifySwitchType"/>
             <item type="array" name="config_networkNotifySwitches"/>
+            <item type="bool" name="config_ongoingSignInNotification"/>
 
         </policy>
     </overlayable>