Fix copilot API payload (#3034)

Author: zetaab

github/copilot.go

@@ -241,9 +241,9 @@ func (s *CopilotService) AddCopilotUsers(ctx context.Context, org string, users
 	u := fmt.Sprintf("orgs/%v/copilot/billing/selected_users", org)
 
 	body := struct {
-		SelectedUsers []string `json:"selected_users"`
+		SelectedUsernames []string `json:"selected_usernames"`
 	}{
-		SelectedUsers: users,
+		SelectedUsernames: users,
 	}
 
 	req, err := s.client.NewRequest("POST", u, body)
@@ -269,9 +269,9 @@ func (s *CopilotService) RemoveCopilotUsers(ctx context.Context, org string, use
 	u := fmt.Sprintf("orgs/%v/copilot/billing/selected_users", org)
 
 	body := struct {
-		SelectedUsers []string `json:"selected_users"`
+		SelectedUsernames []string `json:"selected_usernames"`
 	}{
-		SelectedUsers: users,
+		SelectedUsernames: users,
 	}
 
 	req, err := s.client.NewRequest("DELETE", u, body)

github/copilot_test.go

@@ -680,7 +680,7 @@ func TestCopilotService_AddCopilotUsers(t *testing.T) {
 
 	mux.HandleFunc("/orgs/o/copilot/billing/selected_users", func(w http.ResponseWriter, r *http.Request) {
 		testMethod(t, r, "POST")
-		testBody(t, r, `{"selected_users":["user1","user2"]}`+"\n")
+		testBody(t, r, `{"selected_usernames":["user1","user2"]}`+"\n")
 		fmt.Fprint(w, `{"seats_created": 2}`)
 	})
 
@@ -718,7 +718,7 @@ func TestCopilotService_RemoveCopilotUsers(t *testing.T) {
 
 	mux.HandleFunc("/orgs/o/copilot/billing/selected_users", func(w http.ResponseWriter, r *http.Request) {
 		testMethod(t, r, "DELETE")
-		testBody(t, r, `{"selected_users":["user1","user2"]}`+"\n")
+		testBody(t, r, `{"selected_usernames":["user1","user2"]}`+"\n")
 		fmt.Fprint(w, `{"seats_cancelled": 2}`)
 	})