set_mount_point accepts HTTP headers
Add `cache_control` parameter to `set_mount_point` (#688) * Add `cache_control` parameter to `set_mount_point` Specifies the Cache-Control header value to return when specified. For example: ``` svr.set_mount_point("/assets", "public/assets", "public, max-age=604800, immutable"); ``` * Add default for cache_control Default to "no-cache", which is implicitly what is happening today. * Change set_mount_point to accept Headers * Don't use C++17 destructuring