refactor(auth): Update error status for existing email and username f…

…rom 400 to 409

- Changed response status from 400 (Bad Request) to 409 (Conflict) for:
  - "Email already in use" errors during user registration.
  - "Username already in use" errors during user registration.
- Updated corresponding tests to reflect the new 409 status code.
- Updated documentation to specify the correct error codes for email and username conflicts.

docs/API.md

@@ -124,6 +124,32 @@ The API uses JWT (JSON Web Token) for authentication. To access protected routes
     }
     ```
 
+  - **Status:** `400 Bad Request`
+
+    ```json
+    {
+      "status": "error",
+      "message": "Invalid password.",
+      "error": {
+        "code": "INVALID_PASSWORD",
+        "details": {}
+      }
+    }
+    ```
+
+  - **Status:** `400 Bad Request`
+
+    ```json
+    {
+      "status": "error",
+      "message": "Invalid token.",
+      "error": {
+        "code": "INVALID_TOKEN",
+        "details": {}
+      }
+    }
+    ```
+
   - **Status:** `401 Unauthorized`
 
     ```json
@@ -137,6 +163,45 @@ The API uses JWT (JSON Web Token) for authentication. To access protected routes
     }
     ```
 
+  - **Status:** `500 Internal Server Error`
+
+    ```json
+    {
+      "status": "error",
+      "message": "Error verifying token.",
+      "error": {
+        "code": "VERIFY_TOKEN_ERROR",
+        "details": {}
+      }
+    }
+    ```
+
+  - **Status:** `409 Conflict`
+
+    ```json
+    {
+      "status": "error",
+      "message": "Email already in use.",
+      "error": {
+        "code": "EMAIL_IN_USE",
+        "details": {}
+      }
+    }
+    ```
+
+  - **Status:** `409 Conflict`
+
+    ```json
+    {
+      "status": "error",
+      "message": "Username already in use.",
+      "error": {
+        "code": "USERNAME_IN_USE",
+        "details": {}
+      }
+    }
+    ```
+
   - **Status:** `500 Internal Server Error`
 
     ```json

src/controllers/authController.js

@@ -87,13 +87,13 @@ const completeRegistration = async (req, res) => {
   // Check if the email is already in use
   const existingEmail = await userService.getUserByEmail(email);
   if (existingEmail) {
-    return res.badRequest("Email already in use.", "EMAIL_IN_USE");
+    return res.conflict("Email already in use.", "EMAIL_IN_USE");
   }
 
   // Check if the username is already in use
   const existingUsername = await userService.getUserByUsername(username);
   if (existingUsername) {
-    return res.badRequest("Username already in use.", "USERNAME_IN_USE");
+    return res.conflict("Username already in use.", "USERNAME_IN_USE");
   }
 
   // Create the user

tests/controllers/authController.test.js

@@ -134,7 +134,7 @@ describe("AuthController - completeRegistration", () => {
     expect(res.body.error.code).toBe("INVALID_PASSWORD");
   });
 
-  it("should return 400 if email is already in use", async () => {
+  it("should return 409 if email is already in use", async () => {
     jwtService.verifyToken.mockReturnValue({ email: "test@example.com" });
     validationUtils.validateUsername.mockReturnValue(true);
     validationUtils.validatePassword.mockReturnValue(true);
@@ -148,12 +148,12 @@ describe("AuthController - completeRegistration", () => {
         password: "Password123!",
       });
 
-    expect(res.status).toBe(400);
+    expect(res.status).toBe(409);
     expect(res.body.message).toBe("Email already in use.");
     expect(res.body.error.code).toBe("EMAIL_IN_USE");
   });
 
-  it("should return 400 if username is already in use", async () => {
+  it("should return 409 if username is already in use", async () => {
     jwtService.verifyToken.mockReturnValue({ email: "test@example.com" });
     validationUtils.validateUsername.mockReturnValue(true);
     validationUtils.validatePassword.mockReturnValue(true);
@@ -168,7 +168,7 @@ describe("AuthController - completeRegistration", () => {
         password: "Password123!",
       });
 
-    expect(res.status).toBe(400);
+    expect(res.status).toBe(409);
     expect(res.body.message).toBe("Username already in use.");
     expect(res.body.error.code).toBe("USERNAME_IN_USE");
   });