Do not use shared Discussion

[rerost]

2つ同時にテストが動くと、片方のテストが落ちる

--- PASS: TestFindByURL (0.00s)
    --- PASS: TestFindByURL/#00 (0.26s)
--- PASS: TestIssueFindLastIssue (0.39s)
=== NAME  TestCloseByURL/#00
    discussion_test.go:2[75](https://github.com/rerost/issue-creator/actions/runs/10440886388/job/28911339857#step:4:76): https://github.com/rerost/issue-creator-for-test/discussions/4 is already closed
--- PASS: TestFindLastIssue (0.00s)
    --- PASS: TestFindLastIssue/#00 (0.34s)
=== NAME  TestCloseByURL/#00
    discussion_test.go:292: https://github.com/rerost/issue-creator-for-test/discussions/4 is not close
--- FAIL: TestCloseByURL (0.00s)
    --- FAIL: TestCloseByURL/#00 (1.84s)
--- PASS: TestCreate (0.00s)
    --- PASS: TestCreate/#00 (1.95s)

https://github.com/rerost/issue-creator/actions/runs/10440886388/job/28911339857

[rerost]

たまに

discussion_test.go:104: Could not resolve to a node with the global id of 'D_kwDOJt6V-s4Aa8Js'.

のようにラベルが無いものが返ってくる場合がある

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 37.77%. Comparing base (b2106e4) to head (17c846d).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #147      +/-   ##
==========================================
+ Coverage   37.67%   37.77%   +0.09%     
==========================================
  Files          15       15              
  Lines         629      630       +1     
==========================================
+ Hits          237      238       +1     
  Misses        364      364              
  Partials       28       28              

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