feat(auth): Implement database-backed user authentication and

persistence

This commit introduces a major architectural change by replacing the
previous hardcoded user and data system with a robust, database-driven
approach. It lays the foundation for persistent data storage for all
application models.

Key Changes:

- **Database Integration:** - Added `GORM` and `SQLite` for the database
layer. - The database is now initialized and migrated on application
startup. - Configuration is managed through environment variables
(`DATABASE`, `USERS_FILE`).

- **User Authentication & Management:** - The login endpoint
(`/api/token`) now authenticates users against the database. - JWT
claims are now populated with real user data (`id`, `username`,
`is_superuser`). - Implemented a system to seed the database with
initial users from a `users.json` file.

- **New User API Endpoints:** - `GET /api/users`: Retrieves a list of
all users (superuser access required). - `GET /api/users/user`: Fetches
the data for the currently authenticated user based on their JWT.

- **Data Model Overhaul:** - Refactored all data models (`User`,
`Category`, `Operation`, `Subcategory`) to include GORM tags,
relationships, and a `BaseModel` with auto-generated UUIDs for primary
keys. - Separated user-related structs into `User` (database model),
`AuthRequest` (login payload), and `UserResponse` (safe API response).

- **Middleware & Routing:** - Improved JWT error handling for clearer
client-side messages. - Added a new middleware to allow passing the JWT
in the request body for more flexible client integration.

backend/internal/category/GetAllCategories.go

@@ -5,41 +5,34 @@ import "backend/model"
 func GetAllCategories() ([]model.Category, error) {
 	return []model.Category{
 		{
-			ID:    "1",
 			Title: "Electronics",
 			Icon:  "😀",
 			Type:  "expense",
 		},
 		{
-			ID:    "2",
 			Title: "Clothing",
 			Icon:  "😁",
 			Type:  "expense",
 		},
 		{
-			ID:    "3",
 			Title: "Books",
 			Icon:  "😂",
 			Subcategories: []model.Subcategory{
 				{
-					ID:    "1",
 					Title: "Fiction",
 				},
 				{
-					ID:    "2",
 					Title: "Non-Fiction",
 				},
 			},
 			Type: "expense",
 		},
 		{
-			ID:    "4",
 			Title: "Salary",
 			Icon:  "😀",
 			Type:  "income",
 		},
 		{
-			ID:    "5",
 			Title: "asdf",
 			Icon:  "😀",
 			Type:  "income",

backend/internal/internaljwt/JwtFromBody.go

@@ -0,0 +1,36 @@
+package internaljwt
+
+import (
+	"backend/model"
+
+	"github.com/gofiber/fiber/v2"
+)
+
+func JwtFromBody(c *fiber.Ctx) error {
+	req := new(model.TokenRequest)
+	if err := c.BodyParser(req); err != nil {
+		return c.Status(
+			fiber.StatusBadRequest,
+		).JSON(
+			fiber.Map{
+				"error": "Cannot parse request body",
+			},
+		)
+	}
+
+	if req.Token == "" {
+		return c.Status(
+			fiber.StatusBadRequest,
+		).JSON(
+			fiber.Map{
+				"error": "Token not found in request body",
+			},
+		)
+	}
+
+	c.Request().Header.Set(
+		"Authorization", "Bearer "+req.Token,
+	)
+
+	return c.Next()
+}

backend/internal/operation/GetAllOperation.go

@@ -8,12 +8,13 @@ import (
 func GetAllOperation() ([]model.Operation, error) {
 	return []model.Operation{
 		{
-			ID:       "1",
-			Title:    "Operation 1",
-			Amount:   100,
-			Category: "Category 1",
-			SubCategory: model.Subcategory{
-				ID:    "1",
+			Title:  "Operation 1",
+			Amount: 100,
+			Category: model.Category{
+				Title: "category 1",
+				Type:  "income",
+			},
+			Subcategory: model.Subcategory{
 				Title: "subcategory",
 			},
 			Date: "2022-01-01T00:00:00Z",
@@ -21,30 +22,35 @@ func GetAllOperation() ([]model.Operation, error) {
 			Icon: "😀",
 		},
 		{
-			ID:       "2",
-			Title:    "Operation 2",
-			Amount:   200,
-			Category: "Category 2",
-			Date:     "2022-01-02T00:00:00Z",
-			Type:     "expense",
-			Icon:     "😂",
+			Title:  "Operation 2",
+			Amount: 200,
+			Category: model.Category{
+				Title: "Category 2",
+				Type:  "expense",
+			},
+			Date: "2022-01-02T00:00:00Z",
+			Type: "expense",
+			Icon: "😂",
 		},
 		{
-			ID:       "2",
-			Title:    "Operation 2",
-			Amount:   200,
-			Category: "Category 2",
-			Date:     time.Now().Format(time.RFC3339),
-			Type:     "expense",
-			Icon:     "😂",
+			Title:  "Operation 2",
+			Amount: 200,
+			Category: model.Category{
+				Title: "Category 2",
+				Type:  "expense",
+			},
+			Date: time.Now().Format(time.RFC3339),
+			Type: "expense",
+			Icon: "😂",
 		},
 		{
-			ID:       "1",
-			Title:    "Operation 1",
-			Amount:   100,
-			Category: "Category 1",
-			SubCategory: model.Subcategory{
-				ID:    "1",
+			Title:  "Operation 1",
+			Amount: 100,
+			Category: model.Category{
+				Title: "Category 2",
+				Type:  "expense",
+			},
+			Subcategory: model.Subcategory{
 				Title: "subcategory",
 			},
 			Date: "2022-01-02T00:00:00Z",
@@ -52,22 +58,26 @@ func GetAllOperation() ([]model.Operation, error) {
 			Icon: "😀",
 		},
 		{
-			ID:       "2",
-			Title:    "Operation 2",
-			Amount:   200,
-			Category: "Category 2",
-			Date:     "2022-06-02T00:00:00Z",
-			Type:     "expense",
-			Icon:     "😂",
+			Title:  "Operation 2",
+			Amount: 200,
+			Category: model.Category{
+				Title: "Category 2",
+				Type:  "expense",
+			},
+			Date: "2022-06-02T00:00:00Z",
+			Type: "expense",
+			Icon: "😂",
 		},
 		{
-			ID:       "2",
-			Title:    "Operation 2",
-			Amount:   200,
-			Category: "Category 2",
-			Date:     "2022-06-22T00:00:00Z",
-			Type:     "expense",
-			Icon:     "😂",
+			Title:  "Operation 2",
+			Amount: 200,
+			Category: model.Category{
+				Title: "Category 2",
+				Type:  "expense",
+			},
+			Date: "2022-06-22T00:00:00Z",
+			Type: "expense",
+			Icon: "😂",
 		},
 	}, nil
 }