Refactor Shopping Example: simulate ACLs with LB4 authorization

[raymondfeng]

Describe how to simulate ACLs in Shopping Example

Acceptance criteria

• Illustrate usage of @authorize to add role based access control
• Create an pseudo Authorizer that implements ACL enforcement similar to https://github.com/strongloop/loopback-next/blob/master/examples/access-control-migration
• Create an pseudo Authorizer/Voter that implements custom LB3 role resolver
• Refactor for changes in Extract the jwt authentication to a local component for the auth migration example app #4753
  Extract the jwt authentication to a local component

[deepakrkris]

changing the scope and acceptance criteria to fit Shopping example, because ALL of the action items were accomplished by #4706 and #4571