docs: Improve documentation for isFulfillmentInExercise method

src/models/exercise.php

@@ -119,10 +119,10 @@ public function isFieldInExercise(Field $field): bool
 	}
 
 	/**
-	 * is fulfillment in exercise
-	 *
-	 * @param  Fulfillment $fulfillment
-	 * @return bool
+	 * Check if a fulfillment is part of the exercise.
+	 * 
+	 * @param Fulfillment $fulfillment The fulfillment object to check.
+	 * @return bool Returns true if the fulfillment is part of the exercise, false otherwise.
 	 */
 	public function isFulfillmentInExercise(Fulfillment $fulfillment): bool
 	{