fix(proxy): honor forwarded headers from Caddy

Bump the application version to 1.2.2 and configure forwarded headers so
OpenAPI generates HTTPS URLs when TLS is terminated by Caddy.

CaddyManager/Configurations/Application/ApplicationInfo.cs

@@ -8,7 +8,7 @@ public class ApplicationInfo
     /// <summary>
     /// The version of the application, to be defined and tagged
     /// </summary>
-    public static readonly string Version = "1.2.1";
+    public static readonly string Version = "1.2.2";
 
     /// <summary>
     /// The commit hash of the application

CaddyManager/Program.cs

@@ -1,6 +1,7 @@
 using CaddyManager.Api;
 using CaddyManager.Components;
 using Microsoft.AspNetCore.Components.Server;
+using Microsoft.AspNetCore.HttpOverrides;
 using Microsoft.OpenApi;
 using MudBlazor.Services;
 using NetCore.AutoRegisterDi;
@@ -56,6 +57,19 @@ builder.Services.AddOpenApi(options =>
     });
 });
 
+// Caddy terminates TLS and forwards plain HTTP, so without this the app thinks every request is
+// http and the OpenAPI document advertises http:// server URLs, which the browser blocks as mixed
+// content when the docs page itself was served over https
+builder.Services.Configure<ForwardedHeadersOptions>(options =>
+{
+    options.ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto |
+                               ForwardedHeaders.XForwardedHost;
+    // The proxy is another container on a Docker network, so its address is not known up front;
+    // this app is only ever meant to be reached through that proxy
+    options.KnownIPNetworks.Clear();
+    options.KnownProxies.Clear();
+});
+
 builder.Services.AddMudServices(config =>
 {
     config.SnackbarConfiguration.VisibleStateDuration = 4000;
@@ -65,6 +79,9 @@ builder.Services.AddMudServices(config =>
 
 var app = builder.Build();
 
+// Has to run before anything that reads the scheme, host or client address
+app.UseForwardedHeaders();
+
 // Configure the HTTP request pipeline.
 if (!app.Environment.IsDevelopment())
 {