Add token request parameters for authorization code flow

The access token request needs the code if we're using code flow.
For authorization code flow, grant_type and redirect_uri are also required.

To run tests, pin the minitest version per a conflict with mocha, as noted here:
freerange/mocha#614
But do not leave pinned as the gem fails to install under some rubies that
previously succeeded.

For example:
net-imap-0.5.0 requires ruby version >= 3.1.0, which is incompatible with the
current version, ruby 2.6.8p0 (jruby 9.3.7.0)

lib/omniauth/strategies/openid_connect.rb

@@ -271,6 +271,12 @@ def access_token
           client_auth_method: options.client_auth_method,
         }
 
+        if configured_response_type == 'code'
+          token_request_params[:grant_type] = :authorization_code
+          token_request_params[:code] = authorization_code
+          token_request_params[:redirect_uri] = redirect_uri
+        end
+
         token_request_params[:code_verifier] = params['code_verifier'] || session.delete('omniauth.pkce.verifier') if options.pkce
 
         @access_token = client.access_token!(token_request_params)