This PR is a proposal to improve the situation described in #14750
For some precise commands - we would like to be able to use durations
bigger than hours, minutes..
This PR extends the Duration proposed by Go with :
- `d` - a day or 24hours.
- `y` - a year or 365 days.
I also removed the default value for lifetime and instead fetch the
maxLifetime value from codersdk - so by default if no value set we use
the value defined in the config.
