Archive policy back_window should be a timespan

[jd]

The current value is an integer representing the number of the coarsest granularity in all definitions of an AP. This is not really clear for end users. It should be a regular timespan and rounded to the higher granularity internally.

[chungg]

so if i have a policy of 5s and 1min (let's assume timespan is infinite). if i set 'back_window_timespan' as:

• 6s what happens?
• 62s what happens?

[jd]

If you set 6s, then it would be rounded to 60s (equivalent to back_window = 1). If you set 62s, it'd be 120s (equivalent to back_window = 2).

The rounded timespan would be returned by the API when returning the detail of the created AP, so you know how it has been rounded.