feat(acl): store a diploma in the Documenten API and relate it to the zaak (refs #103)

IZaakGateway.StoreDocumentAsync creates an enkelvoudiginformatieobject (base64
inhoud, buffered non-chunked body, no CRS) and relates it via zaakinformatieobjecten;
AclService.StoreDiplomaAsync default-fills the ZGW document fields (informatieobjecttype,
bronorganisatie, taal nld, creatiedatum); POST /documenten exposes it. Adds the
InformatieobjecttypeUrl default (wired in a following infra commit).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

services/acl/Acl.Application/DocumentRequest.cs

@@ -0,0 +1,17 @@
+namespace Acl.Application;
+
+/// <summary>The fully default-filled diploma document the gateway will create in the ZGW Documenten
+/// API and relate to the zaak (S-10b). <see cref="Inhoud"/> is the raw file content; the gateway
+/// base64-encodes it into the ZGW <c>inhoud</c> field.</summary>
+public sealed record DocumentRequest(
+    string Bronorganisatie,
+    Uri Informatieobjecttype,
+    string Vertrouwelijkheidaanduiding,
+    Uri Zaak,
+    DateOnly Creatiedatum,
+    string Titel,
+    string Auteur,
+    string Taal,
+    string Bestandsnaam,
+    string Formaat,
+    byte[] Inhoud);