Add X-Accel-Buffering: no response header

src/Tgstation.Server.Host/Core/Application.cs

@@ -463,6 +463,9 @@ namespace Tgstation.Server.Host.Core
 			// Add the X-Powered-By response header
 			applicationBuilder.UseServerBranding(assemblyInformationProvider);
 
+			// Add the X-Accel-Buffering response header
+			applicationBuilder.UseDisabledNginxProxyBuffering();
+
 			// suppress OperationCancelledExceptions, they are just aborted HTTP requests
 			applicationBuilder.UseCancelledRequestSuppression();
 

src/Tgstation.Server.Host/Extensions/ApplicationBuilderExtensions.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Globalization;
 using System.Net;
 
@@ -165,6 +165,23 @@ namespace Tgstation.Server.Host.Extensions
 			});
 		}
 
+		/// <summary>
+		/// Add the X-Accel-Buffering response header.
+		/// </summary>
+		/// <param name="applicationBuilder">The <see cref="IApplicationBuilder"/> to configure.</param>
+		/// <remarks>This is used to avoid interruption to SignalR streams by Nginx.</remarks>
+		public static void UseDisabledNginxProxyBuffering(this IApplicationBuilder applicationBuilder)
+		{
+			ArgumentNullException.ThrowIfNull(applicationBuilder);
+
+			// https://www.nginx.com/resources/wiki/start/topics/examples/x-accel/#x-accel-buffering
+			applicationBuilder.Use((context, next) =>
+			{
+				context.Response.Headers.Add("X-Accel-Buffering", "no");
+				return next();
+			});
+		}
+
 		/// <summary>
 		/// Adds additional global <see cref="LogContext"/> to the request pipeline.
 		/// </summary>