Add ability to import yum repositories from disk
As a user, I would like to be able to sync a yum repo from a location other than it's sync url. This is useful if I'm importing a yum repo from a temporary location like a mounted volume.
Specifically, I would like to add a "source" parameter to repositories/:repo_id/sync that temporarily overrides the sync url used by Pulp.
fixes #12459 - allow override of sync url when syncing
This patch allows API callers to pass an optional "source_url" to repo sync.
This allows repos to be synced from locations such as mounted USB volumes
without requiring permenant alteration of the sync URL associated with the