From ca9964f79bd843a1e63137b1d15d08e2680a164d Mon Sep 17 00:00:00 2001
From: Niek Otten <not@respellion.nl>
Date: Mon, 13 Jul 2026 16:45:36 +0200
Subject: [PATCH] feat(domain): add the Ingeschreven state and
 Registration.Approve() (refs #75)

Approve() advances a submitted registration with an opened zaak to INGESCHREVEN;
re-approval and approval-before-zaak are rejected as invalid transitions.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 services/domain/Big.Domain/Registration.cs    | 19 +++++++++++++++++++
 .../domain/Big.Domain/RegistrationStatus.cs   |  7 +++++--
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/services/domain/Big.Domain/Registration.cs b/services/domain/Big.Domain/Registration.cs
index d6f2d85..be1f1ea 100644
--- a/services/domain/Big.Domain/Registration.cs
+++ b/services/domain/Big.Domain/Registration.cs
@@ -64,4 +64,23 @@ public sealed class Registration
 
         ZaakUrl = zaakUrl;
     }
+
+    /// <summary>
+    /// Approve the registration — the behandelaar's decision to enter it in the register. Advances
+    /// <see cref="RegistrationStatus.Ingediend"/> → <see cref="RegistrationStatus.Ingeschreven"/>.
+    /// Requires an opened zaak (the approval sets that zaak's status via the ACL), and only a
+    /// submitted registration can be approved: re-approving is rejected as an invalid transition.
+    /// </summary>
+    public void Approve()
+    {
+        if (ZaakUrl is null)
+            throw new InvalidOperationException(
+                $"Registration {Id} has no zaak yet; it cannot be approved before its zaak is opened.");
+
+        if (Status != RegistrationStatus.Ingediend)
+            throw new InvalidOperationException(
+                $"Registration {Id} is {Status}; only an INGEDIEND registration can be approved.");
+
+        Status = RegistrationStatus.Ingeschreven;
+    }
 }
diff --git a/services/domain/Big.Domain/RegistrationStatus.cs b/services/domain/Big.Domain/RegistrationStatus.cs
index 3ddad57..60bb171 100644
--- a/services/domain/Big.Domain/RegistrationStatus.cs
+++ b/services/domain/Big.Domain/RegistrationStatus.cs
@@ -1,10 +1,13 @@
 namespace Big.Domain;
 
 /// <summary>The lifecycle states a <see cref="Registration"/> moves through. The walking
-/// skeleton knows only <see cref="Ingediend"/>; withdrawal, beoordeling and herregistratie
-/// states arrive in their own slices (Iteration 2+).</summary>
+/// skeleton knows <see cref="Ingediend"/> and the terminal <see cref="Ingeschreven"/>; withdrawal,
+/// beoordeling and herregistratie states arrive in their own slices (Iteration 2+).</summary>
 public enum RegistrationStatus
 {
     /// <summary>Submitted by the zorgprofessional; the registratie process has been started.</summary>
     Ingediend,
+
+    /// <summary>Approved: entered in the register. Terminal in the walking skeleton (S-09b).</summary>
+    Ingeschreven,
 }