This belongs to the OAuth Epic: #4004 - please read this for the big picture of what this issue is for :)

This requires #4180 in order to work.

To make life for theme developers a bit easier it would be nice to add a default entry into the client table for the Ghost front end. A theme developer would be able to use the pre populated client_id to implement custom JavaScript functionality.

To allow JavaScript access out of the box for themes a new client entry would have to be added during migration.