feat: add parseCreatorId helper and integrate into creator ID handlers (#468)

[K1NGD4VID]

Summary

Creator ID params arrive as strings from the URL but are stored as integers in the database. Each handler previously coerced the type independently. This PR adds a shared parseCreatorId helper that parses and validates a creator ID string at the start of every handler that accepts a creator ID.

Closes #468

Changes

New: src/utils/creator-id.utils.ts

• parseCreatorId(raw: string): number — validates input is a positive integer and returns the parsed number. Throws a 400 ApiError (via validationError) for: empty strings, whitespace-only, non-numeric, floats, negatives, and zero.

Modified: src/modules/creators/creators.controllers.ts

• httpGetCreatorStats — replaced manual req.params.id existence/type check with parseCreatorId(req.params.id)

Modified: src/modules/creators/creator-holders.controller.ts

• httpGetCreatorHolders — replaced typeof rawId === string ? rawId : String(rawId ?? ) with parseCreatorId(req.params.id)

Modified: src/modules/webhooks/webhook-signature.middleware.ts

• requireWalletSignature — replaced raw req.params.id extraction + null check with parseCreatorId(req.params.id) (inside try/catch since this middleware lacks async error handling)

New: src/utils/test/creator-id.utils.test.ts

• 10 unit tests covering: valid integer, trimmed integer, float, negative, non-numeric, empty, whitespace-only, trailing non-digits, zero, and statusCode assertion

Acceptance Criteria

• Valid positive integer string parses correctly
• All invalid inputs throw a 400-shaped error
• Helper used consistently across creator detail, holders, and webhook endpoints

Notes

• Buyback quote endpoints do not yet exist in the codebase. The helper is ready to be used when they are added.
• All 10 new unit tests pass. Pre-existing test failures (3 suites) are unrelated to this change (Prisma client generation and implicit any types).

[drips-wave]

@K1NGD4VID Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits