@Override
    public String toString() {
      return name;
    }
The "kid" is fixed. It can be obtained from {@code parameters.getCustomKid()}.

<p>In {@code computeMacAndEncode} Tink writes the "kid" header to the value given by {@code
parameters.getCustomKid()}.

<p>In {@code verifyMacAndDecode} If the kid is present, it needs to match {@code
parameters.getCustomKid()}. If the kid is absent, it will be accepted.

<p>Note: Tink does not allow to randomly generate new {@link JwtHmacKey} objects from
parameters objects with {@code KidStrategy} equals to {@code CUSTOM}.
java_src/src/main/java/com/google/crypto/tink/jwt/JwtHmacParameters.java