feat: add subject and relation api

[everpcpc]

#51

[codecov]

Codecov Report

Attention: Patch coverage is 96.31902% with 6 lines in your changes missing coverage. Please review.

Project coverage is 69.51%. Comparing base (613a4a5) to head (5e7bd89).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
routes/private/routes/subject.ts	96.32%	5 Missing ⚠️
lib/types/fetcher.ts	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #784      +/-   ##
==========================================
+ Coverage   69.27%   69.51%   +0.23%     
==========================================
  Files          95       96       +1     
  Lines       14803    14942     +139     
  Branches      731      740       +9     
==========================================
+ Hits        10255    10387     +132     
- Misses       4539     4546       +7     
  Partials        9        9              

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