Catching common issues here instead of where the caller expects breaks
log formatting, including complete breakage of Special:RecentChanges.
The doc comment says that validation is the caller's responsibility,
which seems like a good idea to me.
Bug: T282070
Change-Id: Ic7e5c5576564e61906a812d50ea4e48adf5ac998
This explores the idea of a PageReference type which represents a
namespace/dbkey pair.
Every ProperPageIdentity is a PageReference. Some LinkTargets can be
mapped to a PageReference.
Bug: T279522
Change-Id: Id8b0c781fce329adcc4770f4840b2ba0108f6898