/**
 * Get the KMS provider identifier associated with this KMS request.
 *
 * This is used to conditionally configure TLS connections based on the KMS
 * request. It is useful for KMIP, which authenticates with a client
 * certificate.
 *
 * @param[in] kms The @ref mongocrypt_kms_ctx_t object.
 * @param[out] len Receives the length of the returned string.
 *
 * @returns One of the NULL terminated static strings: "aws", "azure", "gcp", or
 * "kmip".
 */
MONGOCRYPT_EXPORT
const char *
mongocrypt_kms_ctx_get_kms_provider (mongocrypt_kms_ctx_t *kms, uint32_t *len);