Display a warning to the user when the premitigation doubling time ex…

[ghost]

…ceeds 15 days

Link to issue

• Fixes #555

Changelog entry

When the premitigation doubling time exceeds 15 days, display a subheader to the user prompting to try different parameters.

Additional info

This is my first open-source contribution. Any feedback is welcome :)

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Pull Request Checklist

For Reviewer

• [ ] Submitted under the correct tag
• [ ] Runs without error or warning
• [ ] Documentation revised / included
• [ ] Unit tests included
• [ ] Issues referenced
• [ ] Does not create new bugs / issues

[PhilMiller]

Overall, I think this looks good. Thank you for pitching in!

[DougManuel]

Premitagation and post-mitigation approach of the app is a challenging UI area. All jurisdictions will have an observed doubling time >15 days sooner (hopefully) than later. Yes, that is a post-mitigation double-time - but everywhere now has some sort of mitigation in place.

What we've been doing is using our observed doubling trend from the previous weeks to calculate the current 'effective social distancing'. And then subtract estimate from future, new social distancing scenario.

It is a bit of work to perform. We have suggestions on how the app could be modified for the calculations - if this topic is of interest.

A limitation of the current version is the opposite problem, not allowing a pre-mitigation doubling time large enough. Currently, Rt <1 not allowed.