refactor db accessor

core/nkode/db_accessor.go

@@ -0,0 +1,14 @@
+package nkode
+
+import (
+	"go-nkode/core/model"
+)
+
+type DbAccessor interface {
+	GetCustomer(m.CustomerId) (*Customer, error)
+	GetUser(m.Username, m.CustomerId) (*User, error)
+	WriteNewCustomer(Customer) error
+	WriteNewUser(User) error
+	UpdateUserInterface(m.UserId, UserInterface) error
+	Renew(m.CustomerId) error
+}