Add auth support for UAA IDP

[vuil]

A fair bit of code refactoring to support multiple IDPs, include new support for UAA.

IDP used in CLI context creation is stored in the Context's additionalMetadata map.

context get-token is updated to refresh token based on the IDP associated with said context

tanzu context create / tanzu login
are updated to use UAA IDP unless the CLI recognizes the endpoint as a public Tanzu Platform service endpoint or if CSP idp is explicitly requested with the --force-csp hidden flag.

What this PR does / why we need it

Which issue(s) this PR fixes

Fixes #

Describe testing done for PR

• Ran unit tests

• manual testings of following commands:

1.  > tanzu login --staging --endpoint https://xx--tanzu-hub-endpoint https://yyy

2  > tanzu login 

3. > tanzu login --endpoint https://local-uaa-based-endpoint

4. > ./bin/tanzu context create mytanzuUAA5 -t tanzu --endpoint https://www.alternate.endpoint.com
  [i] Opening the browser window to complete the login
  Log in by visiting this link:

      https://www.alternate.endpoint.com/auth/oauth/authorize?client_id=tp_cli_app&code_challenge=dKfHWRO5hsIVCDFUCDq1g9SjfasXPAeA1rzim7DSDt0&code_challenge_method=S256&redirect_uri=http%3A%2F%2F127.0.0.1%3A57080%2Fcallback&response_type=code&state=575286858256d936f902d73cfe53af31

      Optionally, paste your authorization code: [...]


  [ok] Successfully logged in to 'https://www.alternate.endpoint.com' and created a tanzu context
  > tanzu context current
    Name:            mytanzuUAA5
    Type:            tanzu
    Organization:     ()
    Project:         none set
    Kube Config:     /Users/johndoe/.config/tanzu/kube/config
    Kube Context:    tanzu-cli-mytanzuUAA5

  > ./bin/tanzu login --endpoint https://www.alternate.endpoint.com
  [i] Opening the browser window to complete the login
  Log in by visiting this link:

      https://www.alternate.endpoint.com/auth/oauth/authorize?client_id=tp_cli_app&code_challenge=Zk567ZHRL21Kkp0RpBRbz7QnGaSw9TlD7szg27sHAr4&code_challenge_method=S256&redirect_uri=http%3A%2F%2F127.0.0.1%3A57333%2Fcallback&response_type=code&state=74259704d8911cc27469cb10127f5b29

      Optionally, paste your authorization code: [...]


  [ok] Successfully logged in to 'https://www.alternate.endpoint.com' and created a tanzu context

  > tanzu context current
    Name:            tpsm-c297cb71
    Type:            tanzu
    Project:         none set
    Kube Config:     /Users/johndoe/.config/tanzu/kube/config
    Kube Context:    tanzu-cli-tpsm-c297cb71

5. > tanzu login --endpoint https://dev-csp-based-endpoint --force-csp

6. > tanzu context get-token context_name (for both CSP and UAA-based contexts)

Release note

Add support for using UAA as IDP. After this change, endpoint URIs provided when creating a 'tanzu' context not recognized as public Tanzu SaaS endpoint will default to use UAA as IDP. Use --force-csp boolean flag to override behavior for custom endpoints that still requires CSP.

Additional information

Special notes for your reviewer

[prkalle]

Nice refactoring @vuil !
I am still continuing the review, but sharing few comments i have so far. Thanks

[prkalle]

Changes LGTM, just couple more comments and then good to go.

[anujc25]

OrgName which gets configured in the context as part of additionalMetadata is used by all the plugins to show log messages. Keeping this empty might make the log message incomplete. Does it make sense to configure dummy value as part of additionalMetadata? like SelfManaged or something like that?

[anujc25]

We can do this as part of follow up as well.

[prkalle]

LGTM. Thanks!