refactor: new (simpler) version of the sl library

services/database/database.go

@@ -6,9 +6,9 @@ import (
 	"phc/website/sl"
 )
 
-type Database interface {
-	sl.Service
+var Slot = sl.NewSlot[Database]()
 
+type Database interface {
 	CreateUser(user model.User) error
 	ReadUser(id string) (model.User, error)
 	ReadUsers() ([]model.User, error)
@@ -20,8 +20,6 @@ type Memory struct {
 	Users []model.User
 }
 
-func (m *Memory) Initialize(l *sl.ServiceLocator) error { return nil }
-
 func (m *Memory) CreateUser(user model.User) error {
 	m.Users = append(m.Users, user)
 	return nil