add exception test

[try-agaaain]

#119

Through the lcov tool, I observed that functions such as router::get_name_by_key and rest_rpc::get_error_msg were not covered by tests. These functions will be triggered when exceptions occur, so I added some exception tests.

[github-actions]

Code Coverage Report
for detail, goto summary download Artifacts

Filename                    Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
client_util.hpp                     4                 1    75.00%          25                10    60.00%           4                 2    50.00%
codec.h                             4                 0   100.00%          24                 2    91.67%           0                 0         -
connection.h                       40                 4    90.00%         380                93    75.53%          72                37    48.61%
io_service_pool.h                   5                 0   100.00%          32                 1    96.88%          12                 1    91.67%
md5.hpp                            19                 2    89.47%         127                 8    93.70%          24                 0   100.00%
router.h                           19                 2    89.47%         144                35    75.69%           4                 3    25.00%
rpc_client.hpp                     74                 6    91.89%         669               120    82.06%         132                56    57.58%
rpc_server.h                       28                 3    89.29%         205                20    90.24%          44                10    77.27%
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                             193                18    90.67%        1606               289    82.00%         292               109    62.67%

[try-agaaain]

It seems that the code coverage in the report given by github action has not improved, but there is a slight improvement in the lcov report:

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 90.73482% with 29 lines in your changes are missing coverage. Please review.

Project coverage is 55.57%. Comparing base (44392e4) to head (1883731).

Files	Patch %	Lines
tests/test_rest_rpc.cpp	90.73%	29 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #136      +/-   ##
==========================================
+ Coverage   54.76%   55.57%   +0.80%     
==========================================
  Files         164      163       -1     
  Lines        7945     7939       -6     
==========================================
+ Hits         4351     4412      +61     
+ Misses       3594     3527      -67     

☔ View full report in Codecov by Sentry.
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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
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
client_util.hpp                     4                 1    75.00%          25                10    60.00%           4                 2    50.00%
codec.h                             4                 0   100.00%          24                 2    91.67%           0                 0         -
connection.h                       40                 4    90.00%         380                93    75.53%          72                37    48.61%
io_service_pool.h                   5                 0   100.00%          32                 1    96.88%          12                 1    91.67%
md5.hpp                            19                 2    89.47%         127                 8    93.70%          24                 0   100.00%
router.h                           19                 2    89.47%         144                35    75.69%           4                 3    25.00%
rpc_client.hpp                     74                 6    91.89%         669               120    82.06%         132                56    57.58%
rpc_server.h                       28                 3    89.29%         205                20    90.24%          44                10    77.27%
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                             193                18    90.67%        1606               289    82.00%         292               109    62.67%

[github-actions]

Code Coverage Report
for detail, goto summary download Artifacts

Filename                    Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
client_util.hpp                     4                 1    75.00%          25                10    60.00%           4                 2    50.00%
codec.h                             4                 0   100.00%          24                 2    91.67%           0                 0         -
connection.h                       40                 4    90.00%         380                93    75.53%          72                37    48.61%
io_service_pool.h                   5                 0   100.00%          32                 1    96.88%          12                 1    91.67%
md5.hpp                            19                 2    89.47%         127                 8    93.70%          24                 0   100.00%
router.h                           19                 2    89.47%         144                35    75.69%           4                 3    25.00%
rpc_client.hpp                     74                 6    91.89%         669               120    82.06%         132                56    57.58%
rpc_server.h                       28                 3    89.29%         205                20    90.24%          44                10    77.27%
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                             193                18    90.67%        1606               289    82.00%         292               109    62.67%

[qicosmos]

LGTM