feat: define medium model, media repository

[laminne]

What does this PR do?

• メディアのドメインモデルの定義
• MediaRepositoryの定義

Additional information

• S3互換ストレージでどのようにオブジェクトを特定するのかが不明だったのでpath等は追加していません

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 89 lines in your changes are missing coverage. Please review.

Project coverage is 64.39%. Comparing base (794a861) to head (16fc801).

Files	Patch %	Lines
pkg/drive/model/medium.ts	0.00%	77 Missing ⚠️
pkg/drive/model/repository.ts	0.00%	12 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #396      +/-   ##
==========================================
- Coverage   65.52%   64.39%   -1.13%     
==========================================
  Files          47       49       +2     
  Lines        5076     5165      +89     
  Branches      387      389       +2     
==========================================
  Hits         3326     3326              
- Misses       1750     1839      +89     

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