Implement hashCode/equals on ID for Entities

This also drops an angry comment that was the result of not being able
to fathom the default behaviour.

Fixes #87.

src/main/java/catering/catalog/Consumable.java

@@ -2,6 +2,7 @@
 // SPDX-FileCopyrightText: 2023 swt23w23
 package catering.catalog;
 
+import java.util.Objects;
 import java.util.Optional;
 import java.util.Set;
 
@@ -60,4 +61,16 @@ public class Consumable extends Product {
 		wholesalePrice = price;
 	}
 
+	@Override
+	public int hashCode() {
+		return Objects.hash(Consumable.class, getId());
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (obj instanceof Consumable other) {
+			return getId().equals(other.getId());
+		}
+		return false;
+	}
 }

src/main/java/catering/catalog/Rentable.java

@@ -2,6 +2,7 @@
 // SPDX-FileCopyrightText: 2023 swt23w23
 package catering.catalog;
 
+import java.util.Objects;
 import java.util.Set;
 
 import javax.money.MonetaryAmount;
@@ -48,4 +49,17 @@ public class Rentable extends Product {
 	public MonetaryAmount getPriceForTime(int hours) {
 		return getPrice().multiply(hours).add(getPrice());
 	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(Rentable.class, getId());
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (obj instanceof Rentable other) {
+			return getId().equals(other.getId());
+		}
+		return false;
+	}
 }

src/main/java/catering/order/CustomOrder.java

@@ -16,6 +16,7 @@ import java.time.LocalDateTime;
 import java.time.YearMonth;
 import java.time.format.DateTimeFormatter;
 import java.util.HashSet;
+import java.util.Objects;
 import java.util.Set;
 
 @Entity
@@ -127,4 +128,17 @@ public class CustomOrder extends Order {
 	public void setInvoiceAvailable(boolean available) {
 		this.invoiceAvailable = available;
 	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(CustomOrder.class, getId());
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (obj instanceof CustomOrder other) {
+			return getId().equals(other.getId());
+		}
+		return false;
+	}
 }

src/main/java/catering/orderCatalog/CustomCatalogEntry.java

@@ -8,6 +8,7 @@ import org.salespointframework.quantity.Quantity;
 
 import java.util.Iterator;
 import java.util.Map;
+import java.util.Objects;
 
 @Entity
 public class CustomCatalogEntry {
@@ -77,4 +78,17 @@ public class CustomCatalogEntry {
 	public void setTotalCost(int totalCost) {
 		this.totalCost = totalCost;
 	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(CustomCatalogEntry.class, getId());
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (obj instanceof CustomCatalogEntry other) {
+			return getId() == other.getId();
+		}
+		return false;
+	}
 }

src/main/java/catering/staff/Employee.java

@@ -4,6 +4,8 @@ package catering.staff;
 
 import static org.salespointframework.core.Currencies.EURO;
 
+import java.util.Objects;
+
 import javax.money.MonetaryAmount;
 
 import org.javamoney.moneta.Money;
@@ -58,6 +60,11 @@ public class Employee {
 		this.wage = Money.of(wage, EURO);
 	}
 
+	@Override
+	public int hashCode() {
+		return Objects.hash(Employee.class, getId());
+	}
+
 	@Override
 	public boolean equals(Object obj) {
 		if (obj instanceof Employee other) {

src/main/java/catering/users/User.java

@@ -7,6 +7,8 @@ import jakarta.persistence.GeneratedValue;
 import jakarta.persistence.Id;
 import jakarta.persistence.OneToOne;
 
+import java.util.Objects;
+
 import org.salespointframework.core.AbstractAggregateRoot;
 import org.salespointframework.useraccount.Role;
 import org.salespointframework.useraccount.UserAccount;
@@ -74,23 +76,15 @@ public class User {
 		return userAccount.getRoles().stream().toList().contains(Role.of(role));
 	}
 
-	// Der Ficker muss so. -- sbruder
 	@Override
 	public int hashCode() {
-		final int prime = 31;
-		int result = 1;
-		result = prime * result + ((id == null) ? 0 : id.hashCode());
-		result = prime * result + ((address == null) ? 0 : address.hashCode());
-		result = prime * result + ((fullName == null) ? 0 : fullName.hashCode());
-		result = prime * result + ((userAccount == null) ? 0 : userAccount.getId().hashCode());
-		return result;
+		return Objects.hash(User.class, getId());
 	}
 
 	@Override
 	public boolean equals(Object obj) {
 		if (obj instanceof User other) {
-			return address.equals(other.address) && fullName.equals(other.fullName)
-					&& userAccount.getPassword().equals(other.userAccount.getPassword());
+			return getId().equals(other.getId());
 		}
 		return false;
 	}