Move APIKeys to file and allow read vs read/write

Program.cs

@@ -3,6 +3,7 @@ using Microsoft.Data.Sqlite;
 using TodoApi.Helpers;
 using TodoApi.Models;
 using Microsoft.OpenApi.Models;
+using Newtonsoft.Json;
 
 var builder = WebApplication.CreateBuilder(args);
 
@@ -16,8 +17,20 @@ var connectionString = new SqliteConnectionStringBuilder(builder.Configuration.G
 }.ToString();
 builder.Services.AddDbContext<TodoContext>(options => options.UseSqlite(connectionString));
 
-//setup APIKey validation using APIKeys from config file
-var apiKeys = builder.Configuration.GetSection("Authentication").GetValue<List<string>>("APIKeys");
+//setup APIKey validation using apikey.json file
+ApiKeys apiKeys = new();
+try
+{
+    string? apiKeyFilename = builder.Configuration.GetValue<string>("APIKeyFile");
+    if (File.Exists(apiKeyFilename))
+    {
+        string jsonText = File.ReadAllText(apiKeyFilename);
+
+        ApiKeys? apiKeysTemp = JsonConvert.DeserializeObject<ApiKeys>(jsonText);
+        if (apiKeysTemp != null) apiKeys = apiKeysTemp;
+    }
+}
+catch {}
 builder.Services.AddSingleton<IApiKeyValidator, ApiKeyValidator>(_ => new ApiKeyValidator(apiKeys));
 
 // Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle