Add basic CRUD operations in db/crud.go

Implemented basic CRUD (Create, Read, Update, Delete) operations for users, products, and spend data. These operations allow the other parts of the application to interact with the database, providing fundamental backend functionalities required for user management, product management, and tracking expenses.

db/crud.go

+package db
+
+import "github.com/go-pg/pg/v10"
+
+func AddProduct(db *pg.DB, product *Product) error {
+	_, err := db.Model(product).Insert()
+	return err
+}
+
+func GetProductByID(db *pg.DB, id string) (*Product, error) {
+	product := &Product{}
+	err := db.Model(product).Where("id = ?", id).Select()
+	if err != nil {
+		return nil, err
+	}
+	return product, nil
+}
+
+func UpdateProduct(db *pg.DB, product *Product) error {
+	_, err := db.Model(product).Where("id = ?", product.ID).Update()
+	return err
+}
+
+func AddSpend(db *pg.DB, spend *Spend) error {
+	_, err := db.Model(spend).Insert()
+	return err
+}
+
+func GetSpendByID(db *pg.DB, id string) (*Spend, error) {
+	spend := &Spend{}
+	err := db.Model(spend).Relation("User").Relation("Product").Where("id = ?", id).Select()
+	if err != nil {
+		return nil, err
+	}
+	return spend, nil
+}
+
+func GetUserBySchAcc(db *pg.DB, schacc string) (*User, error) {
+	user := &User{}
+	err := db.Model(user).Relation("Spends").Where("schacc = ?", schacc).Select()
+	if err != nil {
+		return nil, err
+	}
+	return user, nil
+}
+
+// Function to get all users, sorted by name
+func GetUsersSorted(db *pg.DB) ([]*User, error) {
+	var users []*User
+	err := db.Model(&users).Order("name ASC").Select()
+	if err != nil {
+		return nil, err
+	}
+	return users, nil
+}
+
+func UpdateUser(db *pg.DB, user *User) error {
+	_, err := db.Model(user).Where("schacc = ?", user.SchAcc).Update()
+	return err
+}