upgrade compatibility statement

[Cantor, Scott]

> I know I've heard anecdotally that the minor releases (e.g. 3.3.0 -
> 3.3.1) of the IDP are guaranteed compatible, and that the point releases
> (3.2.x -> 3.3.x) are largely compatible and upgrades should be easy and clean
> to perform.

All non-majors are guaranteed compatible unless you mean downgrades, which are only compatible for patches.

Guaranteed doesn't mean we're perfect, it means we'll fix regressions and issue patches as warranted.

https://wiki.shibboleth.net/confluence/display/DEV/Java+Product+Version+Policy

> 	Is this in the wiki anywhere?  I'm trying to write an upgrade
> justification and would like to reference an official statement.

The only justification needed is that if you want security support then you upgrade, always. 3.3.1 is the only supported release as of its release, and 3.2 has been unsupported for months. The only time we have older releases in support is typically across majors, and that will be much shorter in the future simply because the changes won't be as drastic.

-- Scott