Use the Moodle external functions API to retrieve course participants and upload a file via web services

Steps

1. Enable Moodle web services in Site Administration, create a service, add the required functions (core_enrol_get_enrolled_users, core_files_upload), and generate a user token
2. Call core_enrol_get_enrolled_users via REST: POST to /webservice/rest/server.php with wstoken, wsfunction, moodlewsrestformat=json, and courseid as parameters
3. Parse the returned array of user objects, each containing id, fullname, email, roles, and lastcourseaccess
4. To upload a file, call core_files_upload: POST the file content base64-encoded along with component, filearea, filepath, filename, and contextid parameters
5. Capture the itemid returned from the upload response; use it as a draft file reference in subsequent content creation calls
6. Call core_course_get_contents to retrieve the course module structure and verify uploaded content appears in the expected section