mailman3: max_message_size isn't exposed by REST API

[Gunar Schorcht]

Distribution: Ubuntu 18.04.2 LTS
Release: 18.04

mailman3:
  Installiert: 3.1.1-9
  Installationskandidat: 3.1.1-9
  Versionstabelle:
 *** 3.1.1-9 500
        500 http://archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
        100 /var/lib/dpkg/status

Postorius 1.2.4-1 (python3-django-postorius) allows to set `Maximum message size` in `Settings - Message Acceptance`. Because `max_message_size` isn't exposed by REST in Mailman Core version 3.1.1, an error message `Unknown attribute: max_message_size` happens on saving.

The problem is described in [issue](https://gitlab.com/mailman/postorius/issues/246) and was fixed in version [3.2 of Mailman Core](https://gitlab.com/mailman/mailman/merge_requests/329).

Since bionic is the current LTS version, Mailman Core version 3.2.0 should be back-ported to bionic.

[Paride Legovini (paride)]

Hello,

What you are requesting is a Stable Release Update (SRU), which is subject to the policy and procedure documented here:

    https://wiki.ubuntu.com/StableReleaseUpdates

Normally in SRUs upstream version bumps introducing new features are avoided; in this case the specific patch could be cherry-picked, but it still requires special attention due to the risk of regressions (even the simplest change can cause unexpected regressions, see the SRU wiki page for some interesting examples). In other words, while this bug report is valid, fixing it is not a straightforward. I'm not saying it is not doable, but as mailman3 in Bionic is in "universe", it will require an effort from the Ubuntu community.