allow X-Super headers in CORS (#97)

* Addresses ashortsleeves/heckdivers#2

src/Helldivers-2-API/Constants.cs

@@ -0,0 +1,17 @@
+namespace Helldivers.API;
+
+/// <summary>
+/// Contains constant strings used througout the API.
+/// </summary>
+public static class Constants
+{
+    /// <summary>
+    /// The name of the header that identifies the client to the API.
+    /// </summary>
+    public static string CLIENT_HEADER_NAME = "X-Super-Client";
+
+    /// <summary>
+    /// The name of the header with developer contact information.
+    /// </summary>
+    public static string CONTACT_HEADER_NAME = "X-Super-Contact";
+}

src/Helldivers-2-API/Metrics/ClientMetric.cs

@@ -30,7 +30,7 @@ public static string GetClientName(HttpContext context)
             return name;
 
         // If the client sends `X-Super-Client` we use that name
-        if (context.Request.Headers.TryGetValue("X-Super-Client", out var superClient))
+        if (context.Request.Headers.TryGetValue(Constants.CLIENT_HEADER_NAME, out var superClient))
             if (string.IsNullOrWhiteSpace(superClient) is false)
                 return superClient!;
 

src/Helldivers-2-API/Program.cs

@@ -1,3 +1,4 @@
+using Helldivers.API;
 using Helldivers.API.Configuration;
 using Helldivers.API.Controllers;
 using Helldivers.API.Controllers.V1;
@@ -79,6 +80,7 @@
     options.AddDefaultPolicy(policy => policy
         .AllowAnyOrigin()
         .AllowAnyMethod()
+        .WithHeaders(Constants.CLIENT_HEADER_NAME, Constants.CONTACT_HEADER_NAME)
     );
 });