[migration/auth] Migrate https://github.com/strongloop/loopback-example-access-control to LB4

[raymondfeng]

Suggestion

Create an example in LoopBack 4 to illustrate similar access control features as https://github.com/strongloop/loopback-example-access-control. The other option is to add similar features to an existing example such as https://github.com/strongloop/loopback4-example-shopping.

Acceptance criteria

• The example should have ability to authenticate 4 users
  • Use user/user credential DB tables
• Support 4 different roles - guest, owner, team member, administrator
• Authorize different routes against different users/roles
• Document the migration at https://github.com/strongloop/loopback-next/blob/auth-migration/docs/site/migration/auth/example.md

[jannyHou]

PR created in #4571, in progress

[jannyHou]

close after merging #4706
follow up stories:

• Extract the jwt authentication to a local component for the auth migration example app #4753
• 2nd phase improvement for casbin persistence(TBD)
• migrating the models using cli(TBD)