@CanIgnoreReturnValue
    public Builder expectAudience(String value) {
      if (value == null) {
        throw new NullPointerException("audience cannot be null");
      }
      this.expectedAudience = Optional.of(value);
      return this;
    }
Sets the expected audience. When this is set, all tokens that do not contain this audience in
their {@code aud} claims are rejected. When this is not set, all token that have {@code aud}
claims are rejected. So this must be set for token that have {@code aud} claims.

<p>If you want to ignore this claim or if you want to validate it yourself, use
ignoreAudiences().

<p>https://tools.ietf.org/html/rfc7519#section-4.1.3
java_src/src/main/java/com/google/crypto/tink/jwt/JwtValidator.java