enum SupportedHash {
        SHA1, SHA256, SHA512, MD5
    }

    enum EtagStrategy {
        NONE({ null }),
        RAW_SHA1_HEX({ Hashing.sha1().hashBytes(it as byte[]).toString() }),
        NEXUS_ENCODED_SHA1({ "{SHA1{" + Hashing.sha1().hashBytes(it as byte[]) + "}}" })

        private final Closure generator

        EtagStrategy(Closure generator) {
            this.generator = generator
        }