optimize: relation subject create itself.

[chivehao]

• [x] Update the CHANGES log.
• [x] If this pull request closes/resolves/fixes an existing issue, replace the issue number. Closes #.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 45.53%. Comparing base (ac1925c) to head (1773a1a).

Files	Patch %	Lines
...bject/service/impl/SubjectRelationServiceImpl.java	0.00%	6 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #567 +/- ## ============================================ - Coverage 45.55% 45.53% -0.02% Complexity 698 698 ============================================ Files 169 169 Lines 6551 6553 +2 Branches 337 337 ============================================ Hits 2984 2984 - Misses 3467 3469 +2 Partials 100 100 ```

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