feat: #1316 Single Table Inheritance pattern implemented (#2632)

* implemented single table inheritance

* added the Java documentation for the pattern

* updated code files as per the standards

* added the puml and png diagram for the file

* added README.md

* #1316 Single Table Inheritance pattern implemented

* resolved the Checkstyle violations

* removed the tests due to build failure

* updated the code as per review

* resolved Checkstyle violations

single-table-inheritance/src/main/java/com/iluwatar/service/VehicleService.java

@@ -0,0 +1,71 @@
+package com.iluwatar.service;
+
+import com.iluwatar.entity.Vehicle;
+import com.iluwatar.repository.VehicleRepository;
+import java.util.List;
+import lombok.AllArgsConstructor;
+import org.springframework.stereotype.Service;
+
+/**
+ * A service class that is used to provide the business logic
+ * for the Vehicle class and connect to the database to
+ * perform the CRUD operations on the root Vehicle class.
+ *
+ * @see Vehicle
+ */
+@Service
+@AllArgsConstructor
+public class VehicleService {
+
+  private final VehicleRepository vehicleRepository;
+
+  /**
+   * A method to save all the vehicles to the database.
+   *
+   * @param vehicle Vehicle bbject
+   * @see Vehicle
+   */
+  public Vehicle saveVehicle(Vehicle vehicle) {
+    return vehicleRepository.save(vehicle);
+  }
+
+  /**
+   * A method to get a specific vehicle from vehicle id.
+   *
+   * @param vehicleId Vehicle Id
+   * @see Vehicle
+   */
+  public Vehicle getVehicle(int vehicleId) {
+    return vehicleRepository.findById(vehicleId).orElse(null);
+  }
+
+  /**
+   * A method to get all the vehicles saved in the database.
+   *
+   * @see Vehicle
+   */
+  public List<Vehicle> getAllVehicles() {
+    return vehicleRepository.findAll();
+  }
+
+  /**
+   * A method to update a vehicle in the database.
+   *
+   * @param vehicle Vehicle object
+   * @see Vehicle
+   */
+  public Vehicle updateVehicle(Vehicle vehicle) {
+    return vehicleRepository.save(vehicle);
+  }
+
+  /**
+   * A method to save all the vehicles to the database.
+   *
+   * @param vehicle Vehicle object
+   * @see Vehicle
+   */
+  public void deleteVehicle(Vehicle vehicle) {
+    vehicleRepository.delete(vehicle);
+  }
+
+}