Improve reverse proxy

[qicosmos]

  coro_http_server proxy_random(10, 8092);
  proxy_random.set_http_proxy_handler<GET, POST>(
      "/random", {"127.0.0.1:9001", "127.0.0.1:9002", "127.0.0.1:9003"});

  proxy_random.async_start();

  coro_http_client client;
  resp_data result = client.get("http://127.0.0.1:8092/random");

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (00b0d50) 69.65% compared to head (bdf654a) 70.02%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #526      +/-   ##
==========================================
+ Coverage   69.65%   70.02%   +0.37%     
==========================================
  Files         222      221       -1     
  Lines       13506    13486      -20     
==========================================
+ Hits         9407     9443      +36     
+ Misses       4099     4043      -56     

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[github-actions]

Code Coverage Report
for detail, goto summary download Artifacts

Filename                              Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
cinatra_log_wrapper.hpp                       4                 1    75.00%           9                 1    88.89%           0                 0         -
cookie.hpp                                   15                 2    86.67%          84                 2    97.62%          28                 3    89.29%
coro_http_client.hpp                         86                 4    95.35%        1425               204    85.68%         456               116    74.56%
coro_http_connection.hpp                     35                 1    97.14%         650               154    76.31%         192                61    68.23%
coro_http_request.hpp                        27                 4    85.19%         187                16    91.44%          72                10    86.11%
coro_http_response.hpp                       26                 5    80.77%         205                63    69.27%          88                37    57.95%
coro_http_reverse_proxy.hpp                   8                 0   100.00%          74                 4    94.59%           8                 2    75.00%
coro_http_router.hpp                         15                 0   100.00%         188                36    80.85%          20                 8    60.00%
coro_http_server.hpp                         36                 1    97.22%         712                64    91.01%         146                37    74.66%
coro_radix_tree.hpp                          17                 0   100.00%         274                40    85.40%         144                32    77.78%
define.h                                      2                 0   100.00%          28                 2    92.86%          20                 1    95.00%
http_parser.hpp                              25                 4    84.00%         184                30    83.70%          50                12    76.00%
mime_types.hpp                                1                 0   100.00%           7                 2    71.43%           2                 1    50.00%
multipart.hpp                                 4                 0   100.00%          86                13    84.88%          20                 4    80.00%
picohttpparser.h                             14                 6    57.14%         450               277    38.44%         198               101    48.99%
response_cv.hpp                               2                 0   100.00%          55                32    41.82%          46                16    65.22%
session.hpp                                  11                 0   100.00%          54                 2    96.30%           4                 1    75.00%
session_manager.hpp                          10                 1    90.00%          67                 5    92.54%          10                 1    90.00%
sha1.hpp                                     12                 0   100.00%         183                 8    95.63%          12                 2    83.33%
string_resize.hpp                             2                 0   100.00%          18                 0   100.00%           2                 0   100.00%
time_util.hpp                                18                 7    61.11%         154                70    54.55%          26                 2    92.31%
uri.hpp                                      17                 5    70.59%         200                57    71.50%         166                49    70.48%
url_encode_decode.hpp                         4                 0   100.00%          85                20    76.47%          48                16    66.67%
utils.hpp                                    14                 0   100.00%         202                22    89.11%         116                43    62.93%
websocket.hpp                                14                 3    78.57%         174                13    92.53%          78                18    76.92%
ylt/coro_io/channel.hpp                      16                 0   100.00%         104                 9    91.35%          28                 5    82.14%
ylt/coro_io/client_pool.hpp                  22                 4    81.82%         324               173    46.60%          72                46    36.11%
ylt/coro_io/coro_file.hpp                    17                 1    94.12%         162                31    80.86%          42                15    64.29%
ylt/coro_io/coro_io.hpp                      40                 2    95.00%         234                16    93.16%           4                 1    75.00%
ylt/coro_io/detail/client_queue.hpp          10                 5    50.00%          47                23    51.06%          10                 4    60.00%
ylt/coro_io/io_context_pool.hpp              30                 6    80.00%         174                27    84.48%          18                 4    77.78%
ylt/util/concurrentqueue.h                   78                27    65.38%        1241               718    42.14%         290               198    31.72%
ylt/util/expected.hpp                         6                 4    33.33%           6                 4    33.33%           0                 0         -
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                                       638                93    85.42%        8047              2138    73.43%        2416               846    64.98%