feat(workflow): Workflow Client reassigns beoordeling to teamlead (S-14, refs #15)

Implement the BeoordelingEscaleren escalation capability on the Flowable
Workflow Client: acquire escalation jobs, find the still-open Beoordelen task in
the instance and swap its candidate group behandelaar -> teamlead via task
identity links, and complete the job. Segregated onto IBeoordelingEscalatieClient
so the OpenZaak worker is unaffected (ADR-0015).

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

services/domain/Big.Infrastructure/FlowableWorkflowClient.cs

@@ -15,11 +15,14 @@ namespace Big.Infrastructure;
 /// The REST contract here is the one verified against a live flowable-rest engine (ADR-0009).
 /// </summary>
 public sealed class FlowableWorkflowClient(HttpClient http, FlowableOptions options)
-    : IWorkflowClient, IExternalWorkerClient, IUserTaskClient
+    : IWorkflowClient, IExternalWorkerClient, IUserTaskClient, IBeoordelingEscalatieClient
 {
     private const string Topic = "OpenZaakAanmaken";
+    private const string EscalatieTopic = "BeoordelingEscaleren";
     private const string ProcessDefinitionKey = "registratie";
     private const string BeoordelenTaskKey = "Beoordelen";
+    private const string BehandelaarGroup = "behandelaar";
+    private const string TeamleadGroup = "teamlead";
     private const string RegistrationIdVariable = "registrationId";
     private const string ZaakUrlVariable = "zaakUrl";
     private const string BesluitVariable = "besluit";
@@ -106,14 +109,46 @@ public sealed class FlowableWorkflowClient(HttpClient http, FlowableOptions opti
         response.EnsureSuccessStatusCode();
     }
 
-    public Task<IReadOnlyList<EscalatieJob>> AcquireBeoordelingEscalatieJobsAsync(int maxJobs, CancellationToken ct = default)
+    public async Task<IReadOnlyList<EscalatieJob>> AcquireBeoordelingEscalatieJobsAsync(int maxJobs, CancellationToken ct = default)
-        => throw new NotImplementedException();
+    {
+        var request = new AcquireJobsRequest(EscalatieTopic, options.LockDuration, maxJobs, options.WorkerId);
 
-    public Task ReassignBeoordelingToTeamleadAsync(string processInstanceId, CancellationToken ct = default)
+        var jobs = await PostAsync<AcquireJobsRequest, List<AcquiredEscalatieJob>>(
-        => throw new NotImplementedException();
+            "external-job-api/acquire/jobs", request, ct) ?? [];
 
-    public Task CompleteBeoordelingEscalatieJobAsync(string jobId, CancellationToken ct = default)
+        return [.. jobs.Select(job => new EscalatieJob(job.Id, job.ProcessInstanceId))];
-        => throw new NotImplementedException();
+    }
+
+    public async Task ReassignBeoordelingToTeamleadAsync(string processInstanceId, CancellationToken ct = default)
+    {
+        // The escalation token runs in parallel to the still-open Beoordelen task (non-interrupting
+        // boundary timer); find that task in this instance so we can move it to the teamlead. If the
+        // behandelaar completed it just before the timer fired there is nothing to reassign — a
+        // best-effort no-op (the timer/completion race, cf. §8.6).
+        var query = new TaskByInstanceQueryRequest(processInstanceId, BeoordelenTaskKey);
+        var page = await PostAsync<TaskByInstanceQueryRequest, TaskQueryResult>(
+            "service/query/tasks", query, ct);
+
+        var task = page?.Data?.FirstOrDefault();
+        if (task is null)
+            return;
+
+        // Add teamlead, then drop behandelaar: the task now belongs to the teamlead group.
+        using (var added = await SendAsync(
+            $"service/runtime/tasks/{task.Id}/identitylinks",
+            new IdentityLinkRequest(TeamleadGroup, "candidate"), ct))
+            added.EnsureSuccessStatusCode();
+
+        await DeleteAsync(
+            $"service/runtime/tasks/{task.Id}/identitylinks/groups/{BehandelaarGroup}/candidate", ct);
+    }
+
+    public async Task CompleteBeoordelingEscalatieJobAsync(string jobId, CancellationToken ct = default)
+    {
+        using var response = await SendAsync(
+            $"external-job-api/acquire/jobs/{jobId}/complete", new CompleteJobRequest(options.WorkerId, []), ct);
+        response.EnsureSuccessStatusCode();
+    }
 
     private async Task<TResponse?> GetAsync<TResponse>(string path, CancellationToken ct)
     {
@@ -124,6 +159,14 @@ public sealed class FlowableWorkflowClient(HttpClient http, FlowableOptions opti
         return await response.Content.ReadFromJsonAsync<TResponse>(ct);
     }
 
+    private async Task DeleteAsync(string path, CancellationToken ct)
+    {
+        var message = new HttpRequestMessage(HttpMethod.Delete, new Uri(options.BaseUrl, path));
+        message.Headers.Authorization = new AuthenticationHeaderValue("Basic", BasicCredentials());
+        using var response = await http.SendAsync(message, ct);
+        response.EnsureSuccessStatusCode();
+    }
+
     private async Task<TResponse?> PostAsync<TRequest, TResponse>(string path, TRequest body, CancellationToken ct)
     {
         using var response = await SendAsync(path, body, ct);
@@ -163,6 +206,14 @@ public sealed class FlowableWorkflowClient(HttpClient http, FlowableOptions opti
         [property: JsonPropertyName("taskDefinitionKey")] string TaskDefinitionKey,
         [property: JsonPropertyName("includeProcessVariables")] bool IncludeProcessVariables);
 
+    private sealed record TaskByInstanceQueryRequest(
+        [property: JsonPropertyName("processInstanceId")] string ProcessInstanceId,
+        [property: JsonPropertyName("taskDefinitionKey")] string TaskDefinitionKey);
+
+    private sealed record IdentityLinkRequest(
+        [property: JsonPropertyName("group")] string Group,
+        [property: JsonPropertyName("type")] string Type);
+
     private sealed record ClaimTaskRequest(
         [property: JsonPropertyName("action")] string Action,
         [property: JsonPropertyName("assignee")] string Assignee);
@@ -202,6 +253,10 @@ public sealed class FlowableWorkflowClient(HttpClient http, FlowableOptions opti
 
     private sealed record ExecutionDto([property: JsonPropertyName("id")] string Id);
 
+    private sealed record AcquiredEscalatieJob(
+        [property: JsonPropertyName("id")] string Id,
+        [property: JsonPropertyName("processInstanceId")] string ProcessInstanceId);
+
     private sealed record AcquiredJob(
         [property: JsonPropertyName("id")] string Id,
         [property: JsonPropertyName("variables")] IReadOnlyList<Variable> Variables)

services/domain/Big.Infrastructure/IExternalWorkerClient.cs

@@ -16,3 +16,23 @@ public interface IExternalWorkerClient
     /// <summary>Complete an acquired job, passing the opened zaak URL back into the process.</summary>
     Task CompleteOpenZaakJobAsync(string jobId, Uri zaakUrl, CancellationToken ct = default);
 }
+
+/// <summary>
+/// The escalation side of the Workflow Client (S-14): the <c>BeoordelingEscaleren</c> external-worker
+/// jobs parked by the 14-day boundary timer on <c>Beoordelen</c>, and the reassignment they drive.
+/// Kept separate from <see cref="IExternalWorkerClient"/> (interface segregation) so the OpenZaak
+/// worker never sees escalation. Implemented by <see cref="FlowableWorkflowClient"/> — the only code
+/// that talks to Flowable (§8.2, ADR-0015).
+/// </summary>
+public interface IBeoordelingEscalatieClient
+{
+    /// <summary>Acquire and lock up to <paramref name="maxJobs"/> <c>BeoordelingEscaleren</c> jobs.</summary>
+    Task<IReadOnlyList<EscalatieJob>> AcquireBeoordelingEscalatieJobsAsync(int maxJobs, CancellationToken ct = default);
+
+    /// <summary>Reassign the still-open <c>Beoordelen</c> task in the given process instance from the
+    /// behandelaar group to teamlead. Best-effort no-op if the task is no longer open.</summary>
+    Task ReassignBeoordelingToTeamleadAsync(string processInstanceId, CancellationToken ct = default);
+
+    /// <summary>Complete an acquired escalation job so its token reaches the escalation end event.</summary>
+    Task CompleteBeoordelingEscalatieJobAsync(string jobId, CancellationToken ct = default);
+}