ADD: added basic backend function plus a mockup for a cli interface

backend/cmd/cli/user/get.go

@@ -0,0 +1,38 @@
+// cmd/cli/user/get.go
+package user
+
+import (
+	"fmt"
+	// "studia/internal/db"
+	usersvc "studia/internal/user"
+
+	"github.com/spf13/cobra"
+)
+
+var id int64
+
+var getCmd = &cobra.Command{
+	Use:   "get",
+	Short: "Get user by ID",
+	RunE: func(cmd *cobra.Command, args []string) error {
+		database, err := db.New(getDSN())
+		if err != nil {
+			return err
+		}
+
+		service := usersvc.NewService(database)
+		user, err := service.GetByID(id)
+		if err != nil {
+			return err
+		}
+
+		fmt.Printf("ID: %d\nEmail: %s\nName: %s\n",
+			user.ID, user.Email, user.Name)
+		return nil
+	},
+}
+
+func init() {
+	getCmd.Flags().Int64Var(&id, "id", 0, "user ID")
+	getCmd.MarkFlagRequired("id")
+}