Add birthday to runtime_config #30
Description
In light of offspot/metrics#118, while not fixing anything, having a birthday date in runtime_config would allow setting an initial date to the RPI.
This would be set by Imager Service so the birth date of the Pi would be the Image creation time and not the base-image one. That's a little improvement.
It could also be set at anytime of course but the value would be limited considering we already have the hwclock service for that.