protected final boolean isContentTypeAutoDetectionEnabled() {
        if (headers != null && headers.contains(HttpHeaderNames.CONTENT_TYPE)) {
            return false;
        }
        return contentTypeAutoDetectionEnabled;
    }
Sets whether to set the {@code "content-type"} header automatically based on the extension of the file.
core/src/main/java/com/linecorp/armeria/server/file/AbstractHttpFileBuilder.java