@Nullable
    public final String getErrorUri() {
        return errorUri;
    }
A URI identifying a human-readable web page with information about the error, used to provide the client
developer with additional information about the error.
Values for the {@code errorUri} parameter MUST conform to the URI-reference syntax and thus MUST NOT
include characters outside the set {@code %x21} / {@code %x23-5B} / {@code %x5D-7E}.
oauth2/src/main/java/com/linecorp/armeria/common/auth/oauth2/TokenRequestException.java