Add DOTNET_DASHBOARD_CORS_ALLOWED_ORIGINS to app host configuration (#2631)

Author: JamesNK

docs/app-host/configuration.md

@@ -75,6 +75,7 @@ By default, the dashboard is automatically started by the app host. The dashboar
 | `ASPNETCORE_ENVIRONMENT` | `Production` | Configures the environment the dashboard runs as. For more information, see [Use multiple environments in ASP.NET Core](/aspnet/core/fundamentals/environments). |
 | `DOTNET_DASHBOARD_OTLP_ENDPOINT_URL` | `http://localhost:18889` if no gRPC endpoint is configured. | Configures the dashboard OTLP gRPC address. Used by the dashboard to receive telemetry over OTLP. Set on resources as the `OTEL_EXPORTER_OTLP_ENDPOINT` env var. The `OTEL_EXPORTER_OTLP_PROTOCOL` env var is `grpc`.  Automatically generated with _launchSettings.json_ to have a random port on localhost. |
 | `DOTNET_DASHBOARD_OTLP_HTTP_ENDPOINT_URL` | `null` | Configures the dashboard OTLP HTTP address. Used by the dashboard to receive telemetry over OTLP. If only `DOTNET_DASHBOARD_OTLP_HTTP_ENDPOINT_URL` is configured then it is set on resources as the `OTEL_EXPORTER_OTLP_ENDPOINT` env var. The `OTEL_EXPORTER_OTLP_PROTOCOL` env var is `http/protobuf`. |
+| `DOTNET_DASHBOARD_CORS_ALLOWED_ORIGINS` | `null` | Overrides the CORS allowed origins configured in the dashboard. This setting replaces the default behavior of calculating allowed origins based on resource endpoints. |
 | `DOTNET_DASHBOARD_FRONTEND_BROWSERTOKEN` | Automatically generated 128-bit entropy token. | Configures the frontend browser token. This is the value that must be entered to access the dashboard when the auth mode is BrowserToken. If no browser token is specified then a new token is generated each time the app host is launched. |
 
 ## Internal