Roles creation/update responses incorrectly set `null` permissions when not provided.

[ocket8888]

This Bug Report affects these Traffic Control components:

• Traffic Ops

Current behavior:

When the client creates or updates a Role, they may omit the permissions property, or explicitly set it to null. This is implicitly the same as an empty collection, as further GET requests will reveal. However, in those cases, the immediate response to the PUT or POST request in question will show permissions as null.

Expected behavior:

Representations should be consistent, an empty collection is properly represented as an empty collection, not null.

Steps to reproduce:

1. Create or Update a Role, omitting the permissions property thereof in the request payload.

[jammutkarsh]

Hey @ocket8888,
I'm interested in contributing to the Issue and I'd like to learn more about it. I appreciate any information you can provide like and look forward to contributing to the project.
Specifically, can you point out where should I looking for this in the trafic_ops directory?

Thank you,
Utkarsh Chourasia

[ocket8888]

Handlers for /roles requests live in the traffic_ops/traffic_ops_golang/role package