Idempotency Key Validation & Customization

[raghavgopal]

The idempotency can be made configurable based on the users preferences.

• Configurable key validation (format, length, pattern) can be made available to set, something like:

avoonce:
  idempotency:
    key-pattern: "^[a-fA-F0-9\\-]{36}$"  # UUID format
    max-key-length: 128

Also the key validation prevents abuse (overly long keys, injection attempts)

• Some APIs might prefer to send the idempotency-key through query params or JSON-body fields over headers, so this flexibility can be introduced in the library.