private static String joinExposedHeaders(CorsPolicy policy) {
        return joinHeaders(policy.exposedHeaders());
    }
Joins the set of exposed headers into a single string.
This method utilizes {@link #joinHeaders(Set)} to create a comma-separated list of exposed headers.

@return A {@link String} representing the joined exposed headers.
core/src/main/java/com/linecorp/armeria/internal/server/CorsHeaderUtil.java