Per discussion with vivek, some minor UI changes need to happen once JENKINS-41348 is implemented to store credentials in user scope.

Right now the UI makes a POST request to this endpoint when creating a new credential:
/blue/rest/organizations/jenkins/credentials/system/domains/_/credentials/

This URL will likely change to
/blue/rest/organizations/jenkins/credentials/

Credentials are currently fetched via the "search" API and this will be modified to return the proper list of credentials. No UI changes should be necessary there.