feat: implements apis for managing headscale policy (#1792)

hscontrol/types/policy.go

@@ -0,0 +1,20 @@
+package types
+
+import (
+	"errors"
+
+	"gorm.io/gorm"
+)
+
+var (
+	ErrPolicyNotFound         = errors.New("acl policy not found")
+	ErrPolicyUpdateIsDisabled = errors.New("update is disabled for modes other than 'database'")
+)
+
+// Policy represents a policy in the database.
+type Policy struct {
+	gorm.Model
+
+	// Data contains the policy in HuJSON format.
+	Data string
+}