[Checkins] [zopefoundation/Zope] a4d255: Better session documentation and link (#885)

[‮rekcäH nitraM‮]

  Branch: refs/heads/master
  Home:   https://github.com/zopefoundation/Zope
  Commit: a4d255cc78775b03e244b3e2f9c82a2d05e82635
      https://github.com/zopefoundation/Zope/commit/a4d255cc78775b03e244b3e2f9c82a2d05e82635
  Author: ‮rekcäH nitraM‮ <mh at sntl-publishing.com>
  Date:   2020-08-21 (Fri, 21 Aug 2020)

  Changed paths:
    M docs/migrations/zope4/removed.rst

  Log Message:
  -----------
  Better session documentation and link (#885)

* Better session documentation and link

Update seasoning documentation hint and link the chapter on sessions

* - clean up and expand

Co-authored-by: Jens Vagelpohl <jens at netz.ooo>