Implement logout endpoints as per OpenID Connect RP-Initiated Logout 1.0

[t83714]

Implement logout endpoints as per OpenID Connect RP-Initiated Logout 1.0

The similar feature has already been Implemented in: https://github.com/magda-io/magda-auth-okta. Reference:

• https://openid.net/specs/openid-connect-rpinitiated-1_0.html
• https://auth0.com/docs/authenticate/login/logout/log-users-out-of-auth0
• https://developer.okta.com/docs/reference/api/oidc/#logout
• https://developer.okta.com/docs/guides/sign-users-out/nodeexpress/main/

This ticket will:

• adopt the similar implementation
• auto turn on / off logout endpoint by checking OIDC issuer config

Technical Notes:

• Auth0's logout implementations not comfort OIDC spec and not list its endpoint on it's OIDC config
  • we will need to accommodate this

[t83714]

closed via PR: https://github.com/magda-io/magda-auth-oidc/pull/7