Add Mailbox entry into settings

briar-android/artwork/ic_mailbox.svg

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg width="24" height="24" viewBox="0 0 24 24" fill="none" version="1.1" id="svg4"
+    sodipodi:docname="ic_mailbox.svg" inkscape:version="1.1.1 (3bf5ae0d25, 2021-09-20)"
+    xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+    xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+    xmlns="http://www.w3.org/2000/svg">
+  <defs id="defs8" />
+  <sodipodi:namedview id="namedview6" pagecolor="#7d7d7d" bordercolor="#666666" borderopacity="1.0"
+      inkscape:pageshadow="2" inkscape:pageopacity="0" inkscape:pagecheckerboard="0"
+      showgrid="false" inkscape:zoom="9.0780032" inkscape:cx="22.086355" inkscape:cy="10.850404"
+      inkscape:window-width="1920" inkscape:window-height="928" inkscape:window-x="0"
+      inkscape:window-y="108" inkscape:window-maximized="1" inkscape:current-layer="svg4" />
+  <path
+      d="m 5.0781637,2.0000001 c -0.5245356,0 -1.0278314,0.2105185 -1.3987365,0.5847785 C 3.3085215,2.9590375 3.1,3.4663153 3.1,3.9956004 V 16.767666 c 0,0.529289 0.2085215,1.037692 0.5794272,1.411969 0.3709051,0.37423 0.8742009,0.583635 1.3987365,0.583635 H 15.850874 l 3.588966,3.026135 C 20.019297,22.277986 20.9,21.862034 20.9,21.100087 V 3.9956004 C 20.9,3.4663153 20.691473,2.9590375 20.32057,2.5847786 19.949681,2.2105186 19.44635,2.0000001 18.921831,2.0000001 Z M 6.2648311,5.19273 H 17.73517 v 5.65018 h -4.00732 v 1.954238 h 1.465946 c 0.26433,0 0.396594,0.32267 0.209762,0.511253 l -3.160194,3.188138 c -0.11588,0.116871 -0.303625,0.116871 -0.419503,0 L 8.6636588,13.308401 C 8.4767702,13.119818 8.6091068,12.797148 8.8734113,12.797148 H 10.339359 V 10.84291 H 6.2648311 Z"
+      fill="white" id="path2" style="fill:#ffffff;stroke:none;stroke-width:0.590769" />
+</svg>

briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsFragment.java

@@ -36,7 +36,7 @@ public class SettingsFragment extends PreferenceFragmentCompat {
 	private static final String PREF_KEY_FEEDBACK = "pref_key_send_feedback";
 	private static final String PREF_KEY_DEV = "pref_key_dev";
 	private static final String PREF_KEY_EXPLODE = "pref_key_explode";
-	private static final String PREF_KEY_SHARE_APP = "pref_key_share_app";
+	private static final String PREF_KEY_MAILBOX = "pref_key_mailbox";
 
 	@Inject
 	ViewModelProvider.Factory viewModelFactory;
@@ -70,6 +70,17 @@ public class SettingsFragment extends PreferenceFragmentCompat {
 			prefAvatar.setVisible(false);
 		}
 
+		Preference prefMailbox =
+				requireNonNull(findPreference(PREF_KEY_MAILBOX));
+		if (viewModel.shouldEnableMailbox()) {
+			prefMailbox.setOnPreferenceClickListener(preference -> {
+				// TODO show mailbox status/onboarding
+				return true;
+			});
+		} else {
+			prefMailbox.setVisible(false);
+		}
+
 		Preference prefFeedback =
 				requireNonNull(findPreference(PREF_KEY_FEEDBACK));
 		prefFeedback.setOnPreferenceClickListener(preference -> {

briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsViewModel.java

@@ -161,6 +161,10 @@ class SettingsViewModel extends DbViewModel implements EventListener {
 		return featureFlags.shouldEnableProfilePictures();
 	}
 
+	boolean shouldEnableMailbox() {
+		return featureFlags.shouldEnableMailbox();
+	}
+
 	private void loadOwnIdentityInfo() {
 		runOnDbThread(() -> {
 			try {

briar-android/src/main/res/drawable/ic_mailbox.xml

@@ -0,0 +1,12 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:width="24dp"
+	android:height="24dp"
+	android:tint="?android:attr/textColorPrimary"
+	android:viewportWidth="24"
+	android:viewportHeight="24"
+	tools:ignore="NewApi">
+	<path
+		android:fillColor="#ffffff"
+		android:pathData="m5.0782,2c-0.5245,0 -1.0278,0.2105 -1.3987,0.5848C3.3085,2.959 3.1,3.4663 3.1,3.9956V16.7677c0,0.5293 0.2085,1.0377 0.5794,1.412 0.3709,0.3742 0.8742,0.5836 1.3987,0.5836H15.8509l3.589,3.0261C20.0193,22.278 20.9,21.862 20.9,21.1001V3.9956C20.9,3.4663 20.6915,2.959 20.3206,2.5848 19.9497,2.2105 19.4464,2 18.9218,2ZM6.2648,5.1927H17.7352v5.6502h-4.0073v1.9542h1.4659c0.2643,0 0.3966,0.3227 0.2098,0.5113l-3.1602,3.1881c-0.1159,0.1169 -0.3036,0.1169 -0.4195,0L8.6637,13.3084C8.4768,13.1198 8.6091,12.7971 8.8734,12.7971H10.3394V10.8429H6.2648Z" />
+</vector>

briar-android/src/main/res/values/strings.xml

@@ -612,6 +612,9 @@
 	<string name="choose_ringtone_title">Choose ringtone</string>
 	<string name="cannot_load_ringtone">Cannot load ringtone</string>
 
+	<!-- Mailbox -->
+	<string name="mailbox_settings_title">Mailbox</string>
+
 	<!-- Conversation Settings -->
 	<string name="disappearing_messages_title">Disappearing messages</string>
 	<string name="disappearing_messages_explanation_long">Turning on this setting will make new

briar-android/src/main/res/xml/settings.xml

@@ -24,6 +24,11 @@
 		app:fragment="org.briarproject.briar.android.settings.NotificationsFragment"
 		app:icon="@drawable/ic_notifications" />
 
+	<Preference
+		android:key="pref_key_mailbox"
+		android:title="@string/mailbox_settings_title"
+		app:icon="@drawable/ic_mailbox" />
+
 	<PreferenceCategory
 		android:key="pref_key_actions"
 		android:layout="@layout/preferences_category"