Feature/craig/check for downloadmanager before downloading

[CDRussell]

Task/Issue URL: https://app.asana.com/0/414730916066338/1177254132666789
Tech Design URL:
CC:

Description:
Check for DownloadManager being disabled before downloading files to prevent a crash

Useful for testing: being able to go disable DownloadManager

    val intent = Intent(android.provider.Settings.ACTION_APPLICATION_DETAILS_SETTINGS)
    intent.data = Uri.parse("package:com.android.providers.downloads")
    startActivity(intent)

Steps to test this PR:

1. Disable DownloadManager (see above)
2. Attempt to download a file (e.g, http://www.granditaliaperth.co.uk/menus.html and find the download link)
3. Verify the app doesn't crash, and that a snackbar is shown
4. Click on ENABLE
5. Verify download manager app settings screen is shown
6. Enable DownloadManager
7. Try download again

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Internal references:

Software Engineering Expectations
Technical Design Template

[cmonfortep]

LGTM! 👍

[cmonfortep]

I will also approve it 👯‍♀️