Prior to this commit, the policy and priority were hard-coded.
The default values are now the old hard-coded values.
This will allow to develop a cli to trigger forges listing with oneshot policy
and some priority tasks. Thus ingesting those faster and without manual
interventation as we currently do.
Add description in task_dict method because
the only metadata that can be found for a
package at CRAN is its decsription. That can
only br achived from the build in API in R,
which ister is already using. Hence instead of
getting metadata in loader, it is passed
by lister.
