Continuation of Database Migration (Shop)

[ker0olos]

Continuation of #323, re-enables Shop (/buy).

• fix mongodb erroring if character id exists in guild instead of rerolling.
• fix update_topgg_stats.ts db client undefined.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 66.66667% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 65.13%. Comparing base (074bea5) to head (0fb7251). Report is 1 commits behind head on main.

Files	Patch %	Lines
src/gacha.ts	42.85%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #326 +/- ## ========================================== + Coverage 62.86% 65.13% +2.26% ========================================== Files 44 44 Lines 11709 11678 -31 Branches 1004 1036 +32 ========================================== + Hits 7361 7606 +245 + Misses 4334 4058 -276 Partials 14 14 ```

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