fix: access token doesn't generate errors when token expires (#45)

* fix: access token doesn't generate errors when token expires

* refactor: deleted unnecessary spaces

* docs: added extra info

includes/model/class-openedx-woocommerce-plugin-api-calls.php

@@ -127,7 +127,13 @@ public function enrollment_send_request( $enrollment_data, $enrollment_action )
 		}
 
 		$access_token = $this->check_access_token();
-		$user         = $this->get_user( $enrollment_data['enrollment_email'], $access_token );
+
+		// The access token can be an array or not; if it's an array, we need the value at index 1, which contains the generated token.
+		if ( 'array' === gettype( $access_token ) ) {
+			$access_token = $access_token[1];
+		}
+
+		$user = $this->get_user( $enrollment_data['enrollment_email'], $access_token );
 
 		if ( 'error' === $access_token[0] || 'error' === $user[0] ) {
 			if ( 'error' === $access_token[0] && 'error' === $user[0] ) {