Allow setting a personalized number of days

[bedo2991]

I'll open this "issue" as a discussion for an enhancement. First of all, keep up this great work!

As rules are going to change faster than they can be updated in the app for each and every region, it would be good to have a page that allows setting custom rules for the validity of:

• First vaccination
• Full vaccination cycle
• Booster vaccination
• Recovery
• Antigen test (in hours)
• PCR test (in hours)

It would also be good to be able to see what values are currently set for each country or region (for example the recovery certificate in Germany was shortened from 6 to 3 months, it's not clear if the app already considers that or not.

If I can help you support more regions or countries, feel free to let me know.