test(bff): /behandel/werkbak needs a medewerker token with the behandelaar role (refs #13)

Red — the medewerker JWT scheme, the behandelaar policy, and the werkbak endpoint
do not exist yet (endpoint 404s).

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

services/bff/Bff.Tests/TestTokens.cs

@@ -17,6 +17,22 @@ internal static class TestTokens
         new SymmetricSecurityKey(Encoding.UTF8.GetBytes("a-different-signing-key-256-bits-long-indeed-yes!")),
         expired: false);
 
+    /// <summary>A medewerker-realm token carrying the given realm roles under <c>realm_access.roles</c>
+    /// (Keycloak's shape), signed with the valid test key. Used to exercise behandel authorization.</summary>
+    public static string Medewerker(params string[] roles)
+    {
+        var handler = new JsonWebTokenHandler();
+        return handler.CreateToken(new SecurityTokenDescriptor
+        {
+            Claims = new Dictionary<string, object>
+            {
+                ["realm_access"] = new Dictionary<string, object> { ["roles"] = roles },
+            },
+            Expires = DateTime.UtcNow.AddMinutes(30),
+            SigningCredentials = new SigningCredentials(BffFactory.TestSigningKey, SecurityAlgorithms.HmacSha256),
+        });
+    }
+
     private static string Create(string bsn, SymmetricSecurityKey key, bool expired)
     {
         var handler = new JsonWebTokenHandler();