Activate Card

This API is used by D1 to activate a physical card in the issuer backend. <br/><br/> The operation is <b>idempotent</b>: if the card is already active, the request completes successfully and returns <code>204 No Content</code> <br/> This operation does not require a request body. <br/><br/> Security for this endpoint is enforced outside of the OpenAPI contract (for example, via mutual TLS, private network connectivity, or IP allow‑listing).