Add comment per CR

// FREEBIE

SignalServiceKit/src/Messages/Interactions/OWSContact.h

@@ -162,7 +162,9 @@ NSString *NSStringForContactAddressType(OWSContactAddressType value);
 
 #pragma mark - System Contact Conversion
 
+// `contactForSystemContact` does *not* handle avatars. That must be delt with by the caller
 + (nullable OWSContact *)contactForSystemContact:(CNContact *)systemContact;
+
 + (nullable CNContact *)systemContactForContact:(OWSContact *)contact imageData:(nullable NSData *)imageData;
 
 #pragma mark - Proto Serialization

SignalServiceKit/src/Messages/Interactions/OWSContact.m

@@ -558,6 +558,7 @@ NSString *NSStringForContactAddressType(OWSContactAddressType value)
 
 #pragma mark - System Contact Conversion
 
+// `contactForSystemContact` does *not* handle avatars. That must be delt with by the caller
 + (nullable OWSContact *)contactForSystemContact:(CNContact *)systemContact
 {
     if (!systemContact) {