Support for choosing the checksum type in updateinfo
Given errata where the package list has checksums of multiple types, pulp can publish only one of those types, and filter out any others.
When pulp generates updateinfo.xml as part of a yum publish, it has logic for choosing the checksum type(s) based on the checksum(s) in the errata metadata and the checksum type of the repo. For example, if the repo is configured for sha256 and the errata metadata includes both md5 and sha256, pulp will use sha256. For backward-compatibility reasons, it is sometimes needed to use a checksum type in updateinfo that is different than the checksum type of the repo itself. Please have a way to optionally configure a checksum type for updateinfo. When it's not set it can fall back to the checksum type of the repo.