@CanIgnoreReturnValue
    public Builder addNumberClaim(String name, double value) {
      JwtNames.validate(name);
      payload.add(name, new JsonPrimitive(value));
      return this;
    }
Adds a custom claim of type {@code double} to the JWT.
java_src/src/main/java/com/google/crypto/tink/jwt/RawJwt.java