[doc] document deletion lifecycle of collections, and steps to undelete collections
We have some 'Keep collection lifecycle' documentation at https://doc.arvados.org/v2.0/user/tutorials/tutorial-keep-collection-lifecycle.html, which is intended for Arvados users.
We need something similar but more in-depth geared at administrators. It should cover:
a) the various phases of deletion
b) what is necessary to enable deletion (keep-balance and keepstore configuration)
c) what are the flags to tweak the duration of each of the phases of deletion
d) steps to recover collections in each of the phases of deletion (where possible)
For d) we may want to write some code to automate the steps. See also #16427.
Please also review https://doc.arvados.org/v2.0/admin/keep-balance.html which covers some of this ground.
Let's consolidate all this stuff in one place. Note that that last URL is referenced from the 1.3.3 release notes at https://lists.arvados.org/pipermail/arvados/2019-May/000210.html so it should be replaced with a link to the new canonical source, not just deleted.