audit work, fixed StellaOps.sln warnings/errors, fixed tests, sprints work, new advisories

src/Scheduler/StellaOps.Scheduler.WebService/Schedules/ScheduleEndpoints.cs

@@ -1,5 +1,6 @@
 using System.Collections.Immutable;
 using System.ComponentModel.DataAnnotations;
+using System.Globalization;
 using System.Linq;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
@@ -198,7 +199,7 @@ internal static class ScheduleEndpoints
                     ScheduleId: updated.Id,
                     Metadata: new Dictionary<string, string>
                     {
-                        ["updatedAt"] = updated.UpdatedAt.ToString("O")
+                        ["updatedAt"] = updated.UpdatedAt.ToString("O", CultureInfo.InvariantCulture)
                     }),
                 cancellationToken).ConfigureAwait(false);