serializing custom principals

[Cantor, Scott]

> 	In 3.2.1 I do not see the parent shibboleth.DefaultPrincipalSerializers.

In trunk it's in system/conf/general-authn-system.xml

> I think I remember now how this goes for 3.2.x, and that it will be changing in
> 3.3.

Just going by naming, I assume I defined a bean named shibboleth.PrincipalSerializers that can be used to register new ones. Should be documented in the reference tables.

-- Scott