feat: add userinfo & end_session endpoints in configure.sh

[shawnhankim]

Issue Item:

• https://github.com/nginxinc/nginx-openid-connect/issues/58

Background:

• The configure.sh script currently supports to complete the following configuration if an IdP supports OpenID Connect Discovery (usually at the URI /.well-known/openid-configuration).
  • Obtain the URL for jwks_uri or download the JWK file to your NGINX Plus instance
  • Obtain the URL for the authorization endpoint
  • Obtain the URL for the token endpoint
• NGINX Plus OIDC additionally exposed the endpoints of user information and logout in the PR. Hence they need to be configured by using configure.sh.

Description:

• Added two endpoints in the configure.sh to additionally complete the following configuration.
  • Obtain the URL for the user information endpoint of IdP.
  • Obtain the URL for the session end endpoint of IdP.
• Updated README.md in the issue of https://github.com/nginxinc/nginx-openid-connect/issues/55.

Compatibility:

• This PR does not block the existing features as it just adds two endpoints.

[shawnhankim]

• Raised new PR: https://github.com/nginxinc/nginx-openid-connect/pull/61.
• Will reopen if https://github.com/nginxinc/nginx-openid-connect/pull/57 is preferred rather than https://github.com/nginxinc/nginx-openid-connect/pull/60.