feat(2712): remove the accounting service interface from rafiki

[koekiebox]

Story:

https://github.com/interledger/rafiki/issues/2712

Changes proposed in this pull request

• Remove the middleware AccountService

Context

Checklist

• [x] Related issues linked using fixes #number
• [x] Tests added/updated
• [x] Documentation added
• [x] Make sure that all checks pass
• [x] Bruno collection updated

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