Improve loopback4 authorization docs of using the component

[kanusoni]

Hello ,
can you please provide separate demo tutorial for integration of authorization component with loopback4 API.
Whatever written in loopback.io tutorial is bit confusing.....needs more clarification on this.
Thanks.

Acceptance Criteria

• link to access control migration example is missing in authorization docs page
• need to add a few steps on how authorization is used in this example
• need to add a few tutorial steps (like instructing user to add access control to a controller method and check how the example responds) either in authorization docs page or in the example read-me.

Out of scope

• create an authorization example if needed

[jannyHou]

@kanusoni We have a tutorial for the access control example in https://loopback.io/doc/en/lb4/migration-auth-access-control-example.html
It's a tutorial from the migration angle, not exactly the one you want, but it does provide the steps of adding the authorization stuff from scratch.

We will probably create a standalone authorization example for demo.

[dhmlau]

@jannyHou, is it a duplicate of #5294?

[jannyHou]

@dhmlau Let's track authentication and authorization separately, #5294 is for authentication.

[jannyHou]

Thank you @kanusoni , based on the discussion, here is a proposal for adding a new example for authorization and re-structuring the doc:

• Create an authorization overview page (current overview + design section + chain of responsibilities)
• Create a simpler RBAC authorization example
  - scenario: Users are associated with different roles, each role has different access to endpoints, use oauth0 to resolve the role mapping
  - use todo example
  - mount the authorization component
  - specify access control rules for endpoints like @authorize({allowedRoles: [‘admin’]})
  - create a global authorizer to determine the access, use oauth0 service as enforcer
  - create a local voter to define a calculation rule for an endpoint
  - docs of steps
• Create a page for components (The rest of current docs)

[jannyHou]

Done in #6195. Thanks for all suggestions!