Testing issues: Download failures

[crspybits]

I'm getting issues like: https://docs.google.com/document/d/190FBElJHbzCqvI9-pZGuHOg4jC2gbMh3lB6INCaiQcs/edit#bookmark=id.6xpze2glg563

1. I have seen "gone" results from the server:

    "syncserver-message-params" =     (
        "{\"gone\":\"fileRemovedOrRenamed\",\"cloudStorageType\":\"Google\"}"
    );

Each of us using this are using Google Drive I believe. So this reflects a 404 coming back from Google. I don't think I've seen this before. None of the server files have actually been deleted.

2. And also it seems that the server is not responding at all in certain cases. I.e., the file is still downloading in iOSBasics for a very long period of time.

This seems to be an issue due to my use of ngrok, which I believe doesn't respond in certain cases when overloaded.

[crspybits]

I think that this is happening because of my use of the reverse proxy: ngrok to serve requests.

[crspybits]

Test cases:

1. When file is gone (in the DirectoryFileEntry), make sure it's indicated as needing download.
   [DONE]

2. downloadsWith(status:
   [DONE]

[crspybits]

To resolve the second issue I'm going to try changing https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1408153-timeoutintervalforresource
which has a default of 7 days. That seems too long. I think waiting up to a few hours is enough.
Though there is advice from an Apple Tech person to use at least a day. See https://developer.apple.com/forums/thread/101993

See also https://developer.apple.com/documentation/foundation/nsurlsessionconfiguration/1408259-timeoutintervalforrequest

[crspybits]

For timeout issue, I am planning two more changes:

1. In:

    func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {

on an error, I'm going to indicate that the download has to be restarted by the app.

2. I'm going to change the UI so that

a) Images that are not (yet) downloaded cannot be tapped "through" to see the details.

b) Instead, going to prompt the user to see if they want to re-try the download.

[crspybits]

I'm going to hold off on the UI change for now. Downloading is improved and adding complexity to the UI doesn't seem quite merited yet.