## Description
Adds validation of cli inputs for time-based flags.
All time values that can be parsed by the time
handling in common count as supported, even
though official support includes a smaller set.
Also adds some clean-up to time.go and adds a
design document describing standard time value
formats, and the maintenance thereof, in corso.
## Type of change
- [x] 🌻 Feature
- [x] 🗺️ Documentation
- [x] 🤖 Test
## Issue(s)
* #943
* #924
## Test Plan
- [x] ⚡ Unit test
- [x] 💚 E2E
