add shenyu-common dto unit test (#4539)

[comeCU]

Make sure that:

• You have read the contribution guidelines.
• You submit test cases (unit or integration tests) that back your changes.
• Your local test passed ./mvnw clean install -Dmaven.javadoc.skip=true.

[codecov-commenter]

Codecov Report

Merging #4549 (817f473) into master (5149a14) will increase coverage by 0.13%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #4549      +/-   ##
============================================
+ Coverage     68.60%   68.73%   +0.13%     
- Complexity     7703     7725      +22     
============================================
  Files          1033     1033              
  Lines         29575    29575              
  Branches       2673     2673              
============================================
+ Hits          20289    20329      +40     
+ Misses         7698     7650      -48     
- Partials       1588     1596       +8     

see 6 files with indirect coverage changes

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[moremind]

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