[openFATE 305907] Support Update Repo Generation

Feature added by: Adrian Schröter (adrianSuSE) Feature #305907, revision 1, last change by Title: Support Update Repo Generation Buildservice: Evaluation Priority Requester: Desirable Projectmanager: Desirable Requested by: Adrian Schröter (adriansuse) Description: The Build Service should offer update repos as repository channel. It is unclear right now, how we will carry in the extra update information texts. This should maybe designed together with a new changelog handling. -- openSUSE Feature: https://features.opensuse.org/305907