Add read receipts preference.

// FREEBIE

Signal/src/environment/OWSPreferences.h

@@ -52,13 +52,15 @@ extern NSString *const OWSPreferencesKeyEnableDebugLog;
 - (BOOL)hasRegisteredVOIPPush;
 - (void)setHasRegisteredVOIPPush:(BOOL)enabled;
 
-
 - (BOOL)hasDeclinedNoContactsView;
 - (void)setHasDeclinedNoContactsView:(BOOL)value;
 
 - (void)setIOSUpgradeNagVersion:(NSString *)value;
 - (nullable NSString *)iOSUpgradeNagVersion;
 
+- (BOOL)areReadReceiptsEnabled;
+- (void)setAreReadReceiptsEnabled:(BOOL)value;
+
 #pragma mark - Calling
 
 #pragma mark Callkit

Signal/src/environment/OWSPreferences.m

@@ -25,6 +25,7 @@ NSString *const OWSPreferencesKeyCallKitPrivacyEnabled = @"CallKitPrivacyEnabled
 NSString *const OWSPreferencesKeyCallsHideIPAddress = @"CallsHideIPAddress";
 NSString *const OWSPreferencesKeyHasDeclinedNoContactsView = @"hasDeclinedNoContactsView";
 NSString *const OWSPreferencesKeyIOSUpgradeNagVersion = @"iOSUpgradeNagVersion";
+NSString *const OWSPreferencesKeyAreReadReceiptsEnabled = @"areReadReceiptsEnabled";
 
 @implementation OWSPreferences
 
@@ -119,7 +120,6 @@ NSString *const OWSPreferencesKeyIOSUpgradeNagVersion = @"iOSUpgradeNagVersion";
     [self setValueForKey:OWSPreferencesKeyScreenSecurity toValue:@(flag)];
 }
 
-
 - (void)setHasRegisteredVOIPPush:(BOOL)enabled
 {
     [self setValueForKey:OWSPreferencesKeyHasRegisteredVoipPush toValue:@(enabled)];
@@ -155,7 +155,6 @@ NSString *const OWSPreferencesKeyIOSUpgradeNagVersion = @"iOSUpgradeNagVersion";
     [self setValueForKey:OWSPreferencesKeyHasArchivedAMessage toValue:@(enabled)];
 }
 
-
 - (BOOL)hasDeclinedNoContactsView
 {
     NSNumber *preference = [self tryGetValueForKey:OWSPreferencesKeyHasDeclinedNoContactsView];
@@ -178,6 +177,18 @@ NSString *const OWSPreferencesKeyIOSUpgradeNagVersion = @"iOSUpgradeNagVersion";
     return [self tryGetValueForKey:OWSPreferencesKeyIOSUpgradeNagVersion];
 }
 
+- (BOOL)areReadReceiptsEnabled
+{
+    NSNumber *preference = [self tryGetValueForKey:OWSPreferencesKeyAreReadReceiptsEnabled];
+    // Default to NO.
+    return preference ? [preference boolValue] : NO;
+}
+
+- (void)setAreReadReceiptsEnabled:(BOOL)value
+{
+    [self setValueForKey:OWSPreferencesKeyAreReadReceiptsEnabled toValue:@(value)];
+}
+
 #pragma mark - Calling
 
 #pragma mark CallKit