migrate the external pipeline according to the details noted in the parent task (OCMUI-2632):
deploy configurations for long-lived branches.

the openshift template file in the uhc-portal code-repo (deploy/frontend.yaml) needs to be updated, too, to change the repo URL.

we should also update documentation (release to prod' steps) to mention the correct part of the deploy' ref update.

additionally, consider the necessity to address the fact the new GH repo is private; there might be a need to add the authentication.code and/or authentication.image fields to the UI's saas file.
a good example is the hac saas file, which reuses the global definition, and just adds:

authentication: 
  $ref: /services/app-sre/saas-file-auth/global.yml

... which includes/imports this snippet:

image: 
  path: app-interface/global/pull-secret
  field: all
  version: 4
code: 
  path: app-sre/creds/github-app-sre-bot
  field: openshift-saas-deploy

see continuous-delivery-in-app-interface.md for more.