Implemented `deleteMessages` method

parameters:
- chat_id the chat_id of the supergroup or channel
- start first message id to delete
- end last message id to delete
the method will always return `true` as a result, even if the messages 
cannot be deleted
this method does not work on private chat or normal groups
it is not suggested to delete more than 200 messages per call

telegram-bot-api/Client.cpp

@@ -7453,7 +7453,47 @@ td::Status Client::process_get_participants_query(PromisedQueryPtr &query) {
 }
 
 td::Status Client::process_delete_messages_query(PromisedQueryPtr &query) {
-  answer_query(td::JsonFalse(), std::move(query), "Not implemented");
+  auto chat_id = query->arg("chat_id");
+
+  if (chat_id.empty()) {
+    return Status::Error(400, "Chat identifier is not specified");
+  }
+
+  auto start = as_client_message_id(get_message_id(query.get(), "start"));
+  auto end = as_client_message_id(get_message_id(query.get(), "end"));
+
+  if (start == 0 || end == 0) {
+    return Status::Error(400, "Message identifier is not specified");
+  }
+
+  if (start >= end) {
+    return Status::Error(400, "Initial message identifier is not lower than last message identifier");
+  }
+
+  check_chat(chat_id, AccessRights::Write, std::move(query), [this, start, end](int64 chat_id, PromisedQueryPtr query) {
+    if (get_chat_type(chat_id) != ChatType::Supergroup) {
+      return fail_query(400, "Bad Request: method is available only for supergroups", std::move(query));
+    }
+
+    td::vector<td::int64> ids;
+    ids.reserve(200);
+    for (td::int32 i = start; i <= end; i++) {
+      ids.push_back(as_tdlib_message_id(i));
+
+      if (ids.size() == 200) {
+        send_request(make_object<td_api::deleteMessages>(chat_id, std::move(ids), true),
+                     std::make_unique<TdOnOkCallback>());
+        ids.clear();
+      }
+    }
+
+    if (ids.size() != 0) {
+      send_request(make_object<td_api::deleteMessages>(chat_id, std::move(ids), true),
+                   std::make_unique<TdOnOkCallback>());
+    }
+    answer_query(td::JsonTrue(), std::move(query));
+  });
+
   return Status::OK();
 }