Crypto: Add telemetry for events unable to decrypt (UTDs)

#1894

Riot/Analytics/DecryptionFailure.m

@@ -0,0 +1,31 @@
+/*
+ Copyright 2018 New Vector Ltd
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+
+#import "DecryptionFailure.h"
+
+@implementation DecryptionFailure
+
+- (instancetype)init
+{
+    self = [super init];
+    if (self)
+    {
+        _ts = [NSDate date].timeIntervalSince1970;
+    }
+    return self;
+}
+
+@end