Superset API client to create custom roles

[shaidar]

Description/Context

Programmatically create custom Superset role definitions that we can use in conjunction with Moira groups to assign permissions to internal groups accessing the Superset UI.

Plan/Design

Using the following standard roles, create a few custom role definitions that some of our internal clients need for Superset UI access. Then, write a basic script to test out a forked Superset API client to create those new role definitions on our instance of Superset.