refactor(ContactId): Add clone function to ChatId interface

So that History can load history messages without needing to know
what type of Chat the messages are from.

src/core/chatid.h

@@ -41,6 +41,7 @@ public:
     const uint8_t* getData() const;
     bool isEmpty() const;
     virtual int getSize() const = 0;
+    virtual std::unique_ptr<ChatId> clone() const = 0;
 
 protected:
     ChatId();

src/core/groupid.cpp

@@ -67,3 +67,8 @@ int GroupId::getSize() const
 {
     return size;
 }
+
+std::unique_ptr<ChatId> GroupId::clone() const
+{
+    return std::unique_ptr<ChatId>(new GroupId(*this));
+}

src/core/groupid.h

@@ -31,4 +31,5 @@ public:
     explicit GroupId(const QByteArray& rawId);
     explicit GroupId(const uint8_t* rawId);
     int getSize() const override;
+    std::unique_ptr<ChatId> clone() const override;
 };

src/core/toxpk.cpp

@@ -87,3 +87,8 @@ int ToxPk::getSize() const
 {
     return size;
 }
+
+std::unique_ptr<ChatId> ToxPk::clone() const
+{
+    return std::unique_ptr<ChatId>(new ToxPk(*this));
+}

src/core/toxpk.h

@@ -33,4 +33,5 @@ public:
     explicit ToxPk(const uint8_t* rawId);
     explicit ToxPk(const QString& pk);
     int getSize() const override;
+    std::unique_ptr<ChatId> clone() const override;
 };