feat: add Bean Validation annotations to request models

src/main/java/de/zendric/app/xpensely_server/model/AppUserCreateRequest.java

@@ -1,21 +1,25 @@
 package de.zendric.app.xpensely_server.model;
 
-import jakarta.persistence.Column;
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.Pattern;
+import jakarta.validation.constraints.Size;
 import lombok.Data;
 
 @Data
 public class AppUserCreateRequest {
 
-    @Column(name = "username", nullable = false, unique = true)
+    @NotBlank(message = "Username is required")
+    @Size(min = 3, max = 30, message = "Username must be between 3 and 30 characters")
+    @Pattern(regexp = "^[a-zA-Z0-9_.\\-]+$", message = "Username may only contain letters, digits, underscores, dots, and hyphens")
     private String username;
 
+    @NotBlank(message = "Google ID is required")
     private String googleId;
 
     public AppUser convertToAppUser() {
         AppUser appUser = new AppUser();
         appUser.setGoogleId(googleId);
         appUser.setUsername(username);
-
         return appUser;
     }
 }

src/main/java/de/zendric/app/xpensely_server/model/ExpenseChangeRequest.java

@@ -2,6 +2,10 @@ package de.zendric.app.xpensely_server.model;
 
 import java.time.LocalDate;
 
+import jakarta.validation.constraints.DecimalMin;
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.Size;
 import lombok.AllArgsConstructor;
 import lombok.Data;
 import lombok.NoArgsConstructor;
@@ -12,12 +16,25 @@ import lombok.NoArgsConstructor;
 public class ExpenseChangeRequest {
 
     private Long id;
+
+    @NotBlank(message = "Title is required")
+    @Size(max = 100, message = "Title must not exceed 100 characters")
     private String title;
+
+    @NotBlank(message = "Owner name is required")
     private String ownerName;
+
+    @NotNull(message = "Amount is required")
+    @DecimalMin(value = "0.01", message = "Amount must be greater than zero")
     private Double amount;
+
     private Double personalUseAmount;
     private Double otherPersonAmount;
+
+    @NotNull(message = "Date is required")
     private LocalDate date;
+
+    @NotBlank(message = "Category is required")
     private String category;
 
     public Expense convertToExpense(Long userId, ExpenseList expenseList) {

src/main/java/de/zendric/app/xpensely_server/model/ExpenseInput.java

@@ -2,9 +2,10 @@ package de.zendric.app.xpensely_server.model;
 
 import java.time.LocalDate;
 
-import jakarta.persistence.GeneratedValue;
-import jakarta.persistence.GenerationType;
-import jakarta.persistence.Id;
+import jakarta.validation.constraints.DecimalMin;
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.Size;
 import lombok.AllArgsConstructor;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
@@ -16,19 +17,26 @@ import lombok.Setter;
 @NoArgsConstructor
 public class ExpenseInput {
 
-    @Id
-    @GeneratedValue(strategy = GenerationType.IDENTITY)
     private Long id;
 
+    @NotBlank(message = "Title is required")
+    @Size(max = 100, message = "Title must not exceed 100 characters")
     private String title;
 
+    @NotBlank(message = "Owner is required")
     private String owner;
 
+    @NotNull(message = "Amount is required")
+    @DecimalMin(value = "0.01", message = "Amount must be greater than zero")
     private Double amount;
+
     private Double personalUseAmount;
     private Double otherPersonAmount;
 
+    @NotNull(message = "Date is required")
     private LocalDate date;
+
+    @NotBlank(message = "Category is required")
     private String category;
 
     private ExpenseList expenseList;

src/main/java/de/zendric/app/xpensely_server/model/InviteRequest.java

@@ -1,5 +1,7 @@
 package de.zendric.app.xpensely_server.model;
 
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.Size;
 import lombok.AllArgsConstructor;
 import lombok.Data;
 import lombok.NoArgsConstructor;
@@ -8,6 +10,8 @@ import lombok.NoArgsConstructor;
 @AllArgsConstructor
 @NoArgsConstructor
 public class InviteRequest {
+
+    @NotBlank(message = "Invite code is required")
+    @Size(min = 6, max = 6, message = "Invite code must be exactly 6 characters")
     private String inviteCode;
-    private Long userId;
 }