Add feature flag for sharing the app via offline hotspot

bramble-api/src/main/java/org/briarproject/bramble/api/FeatureFlags.java

@@ -12,4 +12,6 @@ public interface FeatureFlags {
 	boolean shouldEnableDisappearingMessages();
 
 	boolean shouldEnableConnectViaBluetooth();
+
+	boolean shouldEnableShareAppViaOfflineHotspot();
 }

bramble-core/src/test/java/org/briarproject/bramble/test/BrambleCoreIntegrationTestModule.java

@@ -43,6 +43,11 @@ public class BrambleCoreIntegrationTestModule {
 			public boolean shouldEnableConnectViaBluetooth() {
 				return true;
 			}
+
+			@Override
+			public boolean shouldEnableShareAppViaOfflineHotspot() {
+				return true;
+			}
 		};
 	}
 }

briar-android/src/main/java/org/briarproject/briar/android/AppModule.java

@@ -305,6 +305,11 @@ public class AppModule {
 			public boolean shouldEnableConnectViaBluetooth() {
 				return IS_DEBUG_BUILD;
 			}
+
+			@Override
+			public boolean shouldEnableShareAppViaOfflineHotspot() {
+				return IS_DEBUG_BUILD;
+			}
 		};
 	}
 }

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

@@ -38,6 +38,7 @@ 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";
 
 	@Inject
 	ViewModelProvider.Factory viewModelFactory;
@@ -84,6 +85,12 @@ public class SettingsFragment extends PreferenceFragmentCompat {
 			PreferenceGroup dev = requireNonNull(findPreference(PREF_KEY_DEV));
 			dev.setVisible(false);
 		}
+
+		if (!viewModel.shouldEnableShareAppViaOfflineHotspot()) {
+			Preference shareApp =
+					requireNonNull(findPreference(PREF_KEY_SHARE_APP));
+			shareApp.setVisible(false);
+		}
 	}
 
 	@Override

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

@@ -262,4 +262,8 @@ class SettingsViewModel extends DbViewModel implements EventListener {
 		return screenLockTimeout;
 	}
 
+	boolean shouldEnableShareAppViaOfflineHotspot() {
+		return featureFlags.shouldEnableShareAppViaOfflineHotspot();
+	}
+
 }

briar-headless/src/main/java/org/briarproject/briar/headless/HeadlessModule.kt

@@ -95,5 +95,6 @@ internal class HeadlessModule(private val appDir: File) {
         override fun shouldEnableProfilePictures() = false
         override fun shouldEnableDisappearingMessages() = false
         override fun shouldEnableConnectViaBluetooth() = false
+        override fun shouldEnableShareAppViaOfflineHotspot() = false
     }
 }

briar-headless/src/test/java/org/briarproject/briar/headless/HeadlessTestModule.kt

@@ -83,6 +83,7 @@ internal class HeadlessTestModule(private val appDir: File) {
         override fun shouldEnableProfilePictures() = false
         override fun shouldEnableDisappearingMessages() = false
         override fun shouldEnableConnectViaBluetooth() = false
+        override fun shouldEnableShareAppViaOfflineHotspot() = false
     }
 
     @Provides