Setup aconfig for communal

This change introduces an aconfig file for communal features, and adds a
first flag which controls the communal hub experience.

Bug: 304584416
Bug: 304585752
Test: verified by adding some local logging code which checks the
communal_hub flag. To turn on and off the flag, I ran: adb shell
device_config put communal com.android.systemui.communal.communal_hub
{true|false}

Change-Id: Ifd9e1f7ca6e103a37d888691a10c1f3d60b7e260
diff --git a/packages/SystemUI/Android.bp b/packages/SystemUI/Android.bp
index ee05f2d..0c92897 100644
--- a/packages/SystemUI/Android.bp
+++ b/packages/SystemUI/Android.bp
@@ -163,6 +163,7 @@
         "SystemUISharedLib",
         "SystemUI-statsd",
         "SettingsLib",
+        "com_android_systemui_communal_flags_lib",
         "com_android_systemui_flags_lib",
         "androidx.core_core-ktx",
         "androidx.viewpager2_viewpager2",
diff --git a/packages/SystemUI/aconfig/Android.bp b/packages/SystemUI/aconfig/Android.bp
index c1390b2..b18c790 100644
--- a/packages/SystemUI/aconfig/Android.bp
+++ b/packages/SystemUI/aconfig/Android.bp
@@ -11,3 +11,16 @@
     name: "com_android_systemui_flags_lib",
     aconfig_declarations: "com_android_systemui_flags",
 }
+
+aconfig_declarations {
+    name: "com_android_systemui_communal_flags",
+    package: "com.android.systemui.communal",
+    srcs: [
+        "communal.aconfig",
+    ],
+}
+
+java_aconfig_library {
+    name: "com_android_systemui_communal_flags_lib",
+    aconfig_declarations: "com_android_systemui_communal_flags",
+}
diff --git a/packages/SystemUI/aconfig/communal.aconfig b/packages/SystemUI/aconfig/communal.aconfig
new file mode 100644
index 0000000..8ecb984
--- /dev/null
+++ b/packages/SystemUI/aconfig/communal.aconfig
@@ -0,0 +1,8 @@
+package: "com.android.systemui.communal"
+
+flag {
+    name: "communal_hub"
+    namespace: "communal"
+    description: "Enables the communal hub experience"
+    bug: "304584416"
+}