Rename SupplierService lookup key to productName for clarity

The service is looked up by product name throughout the codebase, not
an actual product ID as the previous naming implied.

Author: AnveshSrivastava

backends-for-frontends/src/main/java/com/iluwatar/bff/service/SupplierService.java

@@ -36,8 +36,8 @@ public interface SupplierService {
   /**
    * Retrieves supplier stock records for a product.
    *
-   * @param productId identifier of the product to check stock for
+   * @param productName name of the product to check stock for
    * @return the list of supplier stock records for the product
    */
-  List<SupplierRecord> getSupplierRecords(String productId);
+  List<SupplierRecord> getSupplierRecords(String productName);
 }

backends-for-frontends/src/main/java/com/iluwatar/bff/service/impl/InMemorySupplierService.java

@@ -33,19 +33,19 @@
 public final class InMemorySupplierService implements SupplierService {
 
   /** Supplier records stored in memory, keyed by product name. */
-  private final Map<String, List<SupplierRecord>> recordsByProductId;
+  private final Map<String, List<SupplierRecord>> recordsByProductName;
 
   /**
    * Creates the service with a fixed backing map of supplier records, keyed by product name.
    *
    * @param records the supplier data this service serves
    */
   public InMemorySupplierService(final Map<String, List<SupplierRecord>> records) {
-    this.recordsByProductId = records;
+    this.recordsByProductName = records;
   }
 
   @Override
-  public List<SupplierRecord> getSupplierRecords(final String productId) {
-    return recordsByProductId.getOrDefault(productId, List.of());
+  public List<SupplierRecord> getSupplierRecords(final String productName) {
+    return recordsByProductName.getOrDefault(productName, List.of());
   }
 }