Add verification state change messages.

// FREEBIE

src/Messages/Interactions/OWSVerificationStateChangeMessage.h

@@ -0,0 +1,21 @@
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//
+
+#import "OWSRecipientIdentity.h"
+#import "TSInfoMessage.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@class TSThread;
+
+@interface OWSVerificationStateChangeMessage : TSInfoMessage
+
+- (instancetype)initWithTimestamp:(uint64_t)timestamp
+                           thread:(TSThread *)thread
+                verificationState:(OWSVerificationState)verificationState
+                    isLocalChange:(BOOL)isLocalChange;
+
+@end
+
+NS_ASSUME_NONNULL_END

src/Messages/Interactions/OWSVerificationStateChangeMessage.m

@@ -0,0 +1,52 @@
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//
+
+#import "OWSVerificationStateChangeMessage.h"
+#import "OWSDisappearingMessagesConfiguration.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface OWSVerificationStateChangeMessage ()
+
+@property (nonatomic, readonly) OWSVerificationState verificationState;
+@property (nonatomic, readonly) BOOL isLocalChange;
+
+@end
+
+#pragma mark -
+
+@implementation OWSVerificationStateChangeMessage
+
+- (instancetype)initWithTimestamp:(uint64_t)timestamp
+                           thread:(TSThread *)thread
+                verificationState:(OWSVerificationState)verificationState
+                    isLocalChange:(BOOL)isLocalChange
+{
+    self = [super initWithTimestamp:timestamp inThread:thread messageType:TSInfoMessageVerificationStateChange];
+    if (!self) {
+        return self;
+    }
+
+    _verificationState = verificationState;
+    _isLocalChange = isLocalChange;
+
+    return self;
+}
+
+- (NSString *)description
+{
+    switch (self.verificationState) {
+        case OWSVerificationStateDefault:
+        case OWSVerificationStateNoLongerVerified:
+            return NSLocalizedString(@"VERIFICATION_STATE_CHANGE_NOT_VERIFIED",
+                @"Info Message indicating that the verification state is not verified.");
+        case OWSVerificationStateVerified:
+            return NSLocalizedString(@"VERIFICATION_STATE_CHANGE_VERIFIED",
+                @"Info Message indicating that the verification state is verified.");
+    }
+}
+
+@end
+
+NS_ASSUME_NONNULL_END

src/Messages/Interactions/TSInfoMessage.h

@@ -18,6 +18,7 @@ typedef NS_ENUM(NSInteger, TSInfoMessageType) {
     TSInfoMessageTypeGroupQuit,
     TSInfoMessageTypeDisappearingMessagesUpdate,
     TSInfoMessageAddToContactsOffer,
+    TSInfoMessageVerificationStateChange,
 };
 
 + (instancetype)userNotRegisteredMessageInThread:(TSThread *)thread;