make connection_id a string in RPC

It's sent as JSON, so raw binary is not appropriate

src/cryptonote_protocol/cryptonote_protocol_defs.h

@@ -74,7 +74,7 @@ namespace cryptonote
   
 	uint32_t support_flags;
 
-	boost::uuids::uuid connection_id;
+	std::string connection_id;
 
     uint64_t height;
 
@@ -98,7 +98,7 @@ namespace cryptonote
       KV_SERIALIZE(avg_upload)
       KV_SERIALIZE(current_upload)
       KV_SERIALIZE(support_flags)
-      KV_SERIALIZE_VAL_POD_AS_BLOB(connection_id)
+      KV_SERIALIZE(connection_id)
       KV_SERIALIZE(height)
     END_KV_SERIALIZE_MAP()
   };

src/cryptonote_protocol/cryptonote_protocol_handler.inl

@@ -244,7 +244,7 @@ namespace cryptonote
       cnx.current_download = cntxt.m_current_speed_down / 1024;
       cnx.current_upload = cntxt.m_current_speed_up / 1024;
 
-      cnx.connection_id = cntxt.m_connection_id;
+      cnx.connection_id = epee::string_tools::pod_to_hex(cntxt.m_connection_id);
 
       cnx.height = cntxt.m_remote_blockchain_height;
 

src/rpc/core_rpc_server.cpp

@@ -1745,12 +1745,13 @@ namespace cryptonote
       res.peers.push_back({c});
     const cryptonote::block_queue &block_queue = m_p2p.get_payload_object().get_block_queue();
     block_queue.foreach([&](const cryptonote::block_queue::span &span) {
+      const std::string span_connection_id = epee::string_tools::pod_to_hex(span.connection_id);
       uint32_t speed = (uint32_t)(100.0f * block_queue.get_speed(span.connection_id) + 0.5f);
       std::string address = "";
       for (const auto &c: m_p2p.get_payload_object().get_connections())
-        if (c.connection_id == span.connection_id)
+        if (c.connection_id == span_connection_id)
           address = c.address;
-      res.spans.push_back({span.start_block_height, span.nblocks, span.connection_id, (uint32_t)(span.rate + 0.5f), speed, span.size, address});
+      res.spans.push_back({span.start_block_height, span.nblocks, span_connection_id, (uint32_t)(span.rate + 0.5f), speed, span.size, address});
       return true;
     });
 

src/rpc/core_rpc_server_commands_defs.h

@@ -2075,7 +2075,7 @@ namespace cryptonote
     {
       uint64_t start_block_height;
       uint64_t nblocks;
-      boost::uuids::uuid connection_id;
+      std::string connection_id;
       uint32_t rate;
       uint32_t speed;
       uint64_t size;
@@ -2084,7 +2084,7 @@ namespace cryptonote
       BEGIN_KV_SERIALIZE_MAP()
         KV_SERIALIZE(start_block_height)
         KV_SERIALIZE(nblocks)
-        KV_SERIALIZE_VAL_POD_AS_BLOB(connection_id)
+        KV_SERIALIZE(connection_id)
         KV_SERIALIZE(rate)
         KV_SERIALIZE(speed)
         KV_SERIALIZE(size)