remove unused functions

internal/user/store.go

@@ -2,8 +2,7 @@ package user
 
 type UserCRUD interface {
 	Create(user *User) error
-	GetByID(id int64) (*User, error)
-	GetByUsername(username string) (*User, error)
+	GetBy(by, value string) (*User, error)
 	Update(user *User) error
 	Delete(id int64) error
 }