Make the response cacheable

I am not sure if the response contains enough cache data.
Maybe we need to add cache contexts?

The phpcs is wrong: The override of __construct() is not useless, because it adds the protected property $uri.

    if (!$response->headers->has('Content-Type')) {
      $response->headers->set('Content-Type', $file->getMimeType() ?: 'application/octet-stream');
    }

This part is weird.
If we created the response object explicitly in this method, then the check should always return the same result.
Or not?

So do you think we should remove that snippet?

So do you think we should remove that snippet?

Actually I am no longer so sure it is pointless.
The constructor of BinaryFileResponse has the uri as a parameter.
Based on this, it could dynamically set specific headers or not.
Maybe it does set the 'Content-Type' header? I don't see it though.

But you added this code, so you probably had a reason, no?

Either way it would be out of scope for this issue.

Wonder if this is ready for review?

This issue is a blocker for me. I would also like to know if this is ready for testing.

Wonder if this is ready for review?

I don't remember all the details, but at least setting it to review increases the chance of progress :)

So warning caching is my worst.

But applied the change locally and functionality is still there.

Tested on a work site that's using redis and also still working.

Since 2.1.x is still in a beta I'm going to go ahead and include it.