feat: allow configuring OIDC email claim and OIDC auth url parameters (#6867)

This commit:

- Allows configuring the OIDC claim Coder uses for email addresses (by default, this is still email)
- Allows customising the parameters sent to the upstream identity provider when requesting a token. This is still access_type=offline by default.
- Updates documentation related to the above.

cli/server.go

@@ -726,6 +726,8 @@ func (r *RootCmd) Server(newAPI func(context.Context, *coderd.Options) (*coderd.
 					EmailDomain:         cfg.OIDC.EmailDomain,
 					AllowSignups:        cfg.OIDC.AllowSignups.Value(),
 					UsernameField:       cfg.OIDC.UsernameField.String(),
+					EmailField:          cfg.OIDC.EmailField.String(),
+					AuthURLParams:       cfg.OIDC.AuthURLParams.Value,
 					GroupField:          cfg.OIDC.GroupField.String(),
 					GroupMapping:        cfg.OIDC.GroupMapping.Value,
 					SignInText:          cfg.OIDC.SignInText.String(),