Add configuration type binding and implement database connection, disable NativeAOT.

Add: binding setting file items to `AppSettings` class so to provide DI access as `IOptions<OptixServeSettings>`.

Add: EF Core and DbContext to access database in services. This results in disabling NativeAOT due to poor supports for *pre-compiled query*, however many design are optimized for AOT for later re-adoption.

Add: `DesignTimeDbContextFactory` to support EF Core migrations in NativeAOT. (Kept for re-enabling AOT.)

Add: `DbInitializer` for ensuring database connecting in startup.

Add: `ConfigurationHelper.CreateDefaultBuilder()` to read configuration files in default locations. Note this method is currently ONLY used by `DesignTimeDbContextFactory`. Refactor is expected.

Add: `CommonErrorDto` for simple error message.

Add: `VersionEndpoint` ONLY for debugging and testing purpose. Verylikely to be removed in the future.

Other: many utilities and fixes easy to understand.

Note: EF Core migrations are excluded in the early development. Not expected to be added in version control before v1.0 beta.

OptixServe.Api/Configuration/ConfigurationHelper.cs

@@ -0,0 +1,27 @@
+using System;
+
+namespace OptixServe.Api.Configuration;
+
+public static class ConfigurationHelper
+{
+    public static IConfigurationBuilder CreateDefaultBuilder()
+    {
+        var aspEnv = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT");
+        var netEnv = Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT");
+        // Console.WriteLine($"ASPNETCORE_ENVIRONMENT: {aspEnv}, DOTNET_ENVIRONMENT: {netEnv}");
+        var env = aspEnv ?? netEnv ?? null;
+
+        var builder = new ConfigurationBuilder()
+            .SetBasePath(Directory.GetCurrentDirectory())
+            .AddJsonFile("appsettings.json", optional: true)
+            .AddJsonFile("config.json", optional: true);
+        
+        if (env != null)
+        {
+            builder.AddJsonFile($"appsettings.{env}.json", optional: true)
+                .AddJsonFile($"config.{env}.json", optional: true);
+        }
+
+        return builder;
+    }
+}