Allow for different cert expiration intervals to be able to handle shorter lifetime certificates

📑 I have found these related issues/pull requests Various ones related, but not seeing any specifically regarding configuring different intervals based on the cert total lifetime. 🔖 Feature description Allow configuring the expiration warnings either A) based on percentage of life or B) different set of options for shorter lifetimes. Everyone should be used to 90d certs now with LE, but various providers are moving along with offering shorter lifetimes - 30d is pretty commonly available to future proof for the eventual 45 day requirement, but also LE has the 7d certs. When you have a mix of 'max lifetime 200d' and 'short 30d/7d' certs, it's hard to have a reasonable setting. ✔️ Solution Simplest implementation would just be to allow the configuration to be based on percent-of-life instead of fixed days, but it would be nice to have a bit more tuning. i.e. allow "days" and "percent" as suffixes in the dropdown. 7d certs for exampl…