Add Azure Container Apps Jobs telemetry and managed identity support

[Copilot]

Azure Container Apps Jobs need standalone observability and identity support without ASP.NET Core or Dapr dependencies. Short-lived workloads must also flush final telemetry during graceful shutdown.

• Dedicated Jobs package

  • Adds MDev.Dotnet.Azure.ContainerApps.Jobs.
  • Provides additive console and OpenTelemetry registration without clearing consumer providers.
  • Exports logs, traces, and metrics through Azure Monitor.

• Reliable shutdown

  • Flushes all telemetry providers from ApplicationStopped.
  • Enforces a configurable timeout.
  • Preserves the job’s exception and exit code if export fails.

• Managed identity

  • Selects the user-assigned identity from AZURE_CLIENT_ID.
  • Falls back to the system-assigned identity.
  • Rejects malformed configuration without exposing secrets.

• Coverage and guidance

  • Adds configuration, provider composition, identity, and shutdown-export tests.
  • Documents worker lifecycle, cancellation, local development, and Azure deployment.

var builder = Host.CreateApplicationBuilder(args);

builder.Services.AddContainerAppJob(
    builder.Configuration,
    options =>
    {
        options.ServiceName = "DocumentProcessingJob";
        options.EnableAzureMonitor = true;
        options.FlushTimeout = TimeSpan.FromSeconds(10);
    });

builder.Services.AddSingleton(
    builder.Configuration.GetManagedIdentity());

using var host = builder.Build();
await host.RunAsync();

• Fixes Add dedicated Azure Container Apps Jobs support for telemetry and managed identity #77

[mathieumack]

Seems good, need to test now