Can you fullfill this ?
The process of adding redhat repositories is documented.
Quickly, you have to create a subscription allocation with type SAM 1.4 and add the desired subscriptions to it. Then you download the manifest and add it to the foreman.
From there you can add the repos in Content> Redhat repos. It then appears in the products, it only remains to sync.
Notes the redhat repos available are directly linked to the subscriptions added in the manifest.
If you use a proxy, you can enter it in Settings> General.