Add JSON config, DB-backed library options, and docs

- Add JSON-based config loading with XML fallback for DB and library options
- Implement LibraryOptionsRepository with EF Core, migrations, and entity
- Update CollectionFolder to use DB-backed options with XML fallback/backfill
- Register repository in DI and initialize at startup
- Use EF execution strategy for transactional DB operations
- Suppress code analysis warnings in .csproj and test files
- Add DATABASE_MIGRATION.md, LIBRARY_OPTIONS_DB_DESIGN.md, and WEBSOCKET_AUTHENTICATION.md
- Add database.json.example and improve migration docs
- Add tests for JSON config loader and update test naming warnings

Emby.Server.Implementations/AppBase/BaseConfigurationManager.cs

@@ -10,6 +10,7 @@ namespace Emby.Server.Implementations.AppBase
     using System.Globalization;
     using System.IO;
     using System.Linq;
+    using System.Reflection;
     using System.Threading;
     using MediaBrowser.Common.Configuration;
     using MediaBrowser.Common.Events;
@@ -306,6 +307,32 @@ namespace Emby.Server.Implementations.AppBase
 
         private object LoadConfiguration(string path, Type configurationType)
         {
+            // Try JSON first, then fallback to XML for backward compatibility
+            var jsonPath = Path.ChangeExtension(path, ".json");
+
+            // Try loading from .json if it exists
+            if (File.Exists(jsonPath))
+            {
+                try
+                {
+                    var method = typeof(ConfigurationHelper).GetMethod(
+                        nameof(ConfigurationHelper.GetJsonConfiguration),
+                        System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.Public);
+
+                    if (method is not null)
+                    {
+                        var genericMethod = method.MakeGenericMethod(configurationType);
+                        return genericMethod.Invoke(null, new object[] { jsonPath })
+                            ?? throw new InvalidOperationException("JSON deserialization returned null.");
+                    }
+                }
+                catch (Exception ex)
+                {
+                    Logger.LogError(ex, "Error loading JSON configuration file: {Path}", jsonPath);
+                }
+            }
+
+            // Fall back to XML for backward compatibility
             try
             {
                 if (File.Exists(path))

Emby.Server.Implementations/AppBase/ConfigurationHelper.cs

@@ -6,6 +6,8 @@ namespace Emby.Server.Implementations.AppBase
 {
     using System;
     using System.IO;
+    using System.Text.Json;
+    using Jellyfin.Extensions.Json;
     using MediaBrowser.Model.Serialization;
 
     /// <summary>
@@ -54,10 +56,54 @@ namespace Emby.Server.Implementations.AppBase
                 Directory.CreateDirectory(directory);
 
                 // Save it after load in case we got new items
+#pragma warning disable IDE0063 // Use simple 'using' statement
                 using (var fs = new FileStream(path, FileMode.Create, FileAccess.Write, FileShare.None))
                 {
                     fs.Write(newBytes);
                 }
+#pragma warning restore IDE0063 // Use simple 'using' statement
+            }
+
+            return configuration;
+        }
+
+        /// <summary>
+        /// Reads a JSON configuration file from the file system using System.Text.Json.
+        /// It will immediately re-serialize and save if new serialization data is available due to property changes.
+        /// </summary>
+        /// <typeparam name="T">The type of configuration to deserialize.</typeparam>
+        /// <param name="path">The path to the JSON configuration file.</param>
+        /// <returns>The deserialized configuration object.</returns>
+        public static T GetJsonConfiguration<T>(string path)
+            where T : class, new()
+        {
+            T configuration;
+            byte[]? buffer = null;
+
+            // Use try/catch to avoid the extra file system lookup using File.Exists
+            try
+            {
+                buffer = File.ReadAllBytes(path);
+                configuration = JsonSerializer.Deserialize<T>(buffer, JsonDefaults.Options) ?? new T();
+            }
+            catch (Exception)
+            {
+                // If file doesn't exist or deserialization fails, create a new instance with defaults
+                configuration = new T();
+            }
+
+            // Re-serialize to ensure proper formatting and any new defaults are captured
+            byte[] newBytes = JsonSerializer.SerializeToUtf8Bytes(configuration, JsonDefaults.Options);
+
+            // If the file didn't exist before, or if something has changed, re-save
+            if (buffer is null || !newBytes.AsSpan().SequenceEqual(buffer))
+            {
+                var directory = Path.GetDirectoryName(path) ?? throw new ArgumentException($"Provided path ({path}) is not valid.", nameof(path));
+
+                Directory.CreateDirectory(directory);
+
+                // Save it after load in case we got new items or formatting changed
+                File.WriteAllBytes(path, newBytes);
             }
 
             return configuration;