Deprecate Instant.period

[bonjourmauko]

Depends on #1160

Deprecations

• In periods.Instant:
  • Remove period, method used to build a Period from an Instant.
  • This method created an upward circular dependency between Instant and Period causing lots of trouble.
  • The functionality is still provided by periods.period and the Period constructor.

Migration details

• Replace some_period.start.period and similar methods with Period((unit, some_period.start, 1)).

[MattiSG]

I will postpone reviewing this PR until the one it depends on is approved, and suggest that this one is set to draft. Indeed, I fail to see how it could be approved when #1141 might not go through.

Do you truly need #1141 for this one to be reviewed? 🙂 As an alternative to switching to draft, I suggest to remove the dependency and rebase straight on master. Yes, test-docs might fail until #1141 is fixed, but that is true of all PRs, not only of this one. This would enable reviews to be parallelised and proper solutions found for #1140 without blocking all the others.

[bonjourmauko]

cc @MattiSG