docs: added docs to explain some lines of code

includes/model/class-openedx-woocommerce-plugin-enrollment.php

@@ -348,10 +348,10 @@ public function save_enrollment( $post, $enrollment_arr, $enrollment_action, $or
 			$this->update_post( $post_id );
 		}
 
-		$non_valid_statuses      = array( 'enrollment-success', 'enrollment-pending', 'enrollment-error' );
 		$api                     = new Openedx_Woocommerce_Plugin_Api_Calls();
 		$enrollment_api_response = $api->request_handler( $enrollment_data, $enrollment_action );
 
+		// The $enrollment_api_response[0] is the status of the request.
 		$this->update_post( $post_id, $enrollment_api_response[0] );
 		$this->log_manager->create_change_log( $post_id, $old_data, $enrollment_data, $enrollment_action, $enrollment_api_response );
 

includes/model/class-openedx-woocommerce-plugin-log.php

@@ -85,6 +85,9 @@ public function check_api_response( $response ) {
 				return $response_message;
 
 			case 'success':
+				// Convert the response to JSON to be able to display it in the log.
+				// The json_decode is needed to convert the response (string) to an asociative array.
+				// The json_encode is needed to convert the asociative array to a JSON and be able to access the variables.
 				return wp_json_encode( json_decode( $response_message, true ) );
 
 			case 'not_api':