Set default request accept headers

Jellyfin.Server/Startup.cs

@@ -66,10 +66,14 @@ namespace Jellyfin.Server
             var productHeader = new ProductInfoHeaderValue(
                 _serverApplicationHost.Name.Replace(' ', '-'),
                 _serverApplicationHost.ApplicationVersionString);
+            var acceptJsonHeader = new MediaTypeWithQualityHeaderValue(MediaTypeNames.Application.Json);
+            var acceptAnyHeader = new MediaTypeWithQualityHeaderValue("*/*");
             services
                 .AddHttpClient(NamedClient.Default, c =>
                 {
                     c.DefaultRequestHeaders.UserAgent.Add(productHeader);
+                    c.DefaultRequestHeaders.Accept.Add(acceptJsonHeader);
+                    c.DefaultRequestHeaders.Accept.Add(acceptAnyHeader);
                 })
                 .ConfigurePrimaryHttpMessageHandler(x => new DefaultHttpClientHandler());
 
@@ -77,6 +81,8 @@ namespace Jellyfin.Server
                 {
                     c.DefaultRequestHeaders.UserAgent.Add(productHeader);
                     c.DefaultRequestHeaders.UserAgent.Add(new ProductInfoHeaderValue($"({_serverApplicationHost.ApplicationUserAgentAddress})"));
+                    c.DefaultRequestHeaders.Accept.Add(acceptJsonHeader);
+                    c.DefaultRequestHeaders.Accept.Add(acceptAnyHeader);
                 })
                 .ConfigurePrimaryHttpMessageHandler(x => new DefaultHttpClientHandler());