Spike: what happens when the Jetpack "master user" changes?

Determine what happens if the Jetpack master user changes.

Write up an issue for the work needed to gracefully handle this user change.

See: https://github.com/Automattic/jetpack/search?utf8=%E2%9C%93&q=master_user

Start with the Jetpack search for “master_user” linked in the issue and trace how the master user is currently handled. Document what happens when that user changes, then create a follow-up issue describing the work needed to handle the change gracefully.

Written by the indexing model from the issue text.