sock: change Sock::SendComplete() to take Span

This would make it easier to pass other than `std::string` types,
to be used in the `Socks5()` function.

src/util/sock.cpp

@@ -242,7 +242,7 @@ bool Sock::WaitMany(std::chrono::milliseconds timeout, EventsPerSock& events_per
 #endif /* USE_POLL */
 }
 
-void Sock::SendComplete(const std::string& data,
+void Sock::SendComplete(Span<const unsigned char> data,
                         std::chrono::milliseconds timeout,
                         CThreadInterrupt& interrupt) const
 {
@@ -283,6 +283,13 @@ void Sock::SendComplete(const std::string& data,
     }
 }
 
+void Sock::SendComplete(Span<const char> data,
+                        std::chrono::milliseconds timeout,
+                        CThreadInterrupt& interrupt) const
+{
+    SendComplete(MakeUCharSpan(data), timeout, interrupt);
+}
+
 std::string Sock::RecvUntilTerminator(uint8_t terminator,
                                       std::chrono::milliseconds timeout,
                                       CThreadInterrupt& interrupt,

src/util/sock.h

@@ -228,7 +228,14 @@ public:
      * @throws std::runtime_error if the operation cannot be completed. In this case only some of
      * the data will be written to the socket.
      */
-    virtual void SendComplete(const std::string& data,
+    virtual void SendComplete(Span<const unsigned char> data,
+                              std::chrono::milliseconds timeout,
+                              CThreadInterrupt& interrupt) const;
+
+    /**
+     * Convenience method, equivalent to `SendComplete(MakeUCharSpan(data), timeout, interrupt)`.
+     */
+    virtual void SendComplete(Span<const char> data,
                               std::chrono::milliseconds timeout,
                               CThreadInterrupt& interrupt) const;