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/Endpoints/VersionEndpoint.cs

@@ -0,0 +1,35 @@
+using System.Text.Json.Serialization;
+using Microsoft.Extensions.Options;
+using OptixServe.Api.Configuration;
+using OptixServe.Api.Dtos;
+
+namespace OptixServe.Api.Endpoints;
+
+
+[JsonSerializable(typeof(string))]
+[JsonSerializable(typeof(CommonErrorDto))]
+public partial class VersionJsonContext : JsonSerializerContext { }
+
+
+/// <summary>
+/// This is a endpoint ONLY FOR TEST!
+/// Should not expect ANY stable behavior on it!
+/// </summary>
+public static class VersionEndpoint
+{
+    public static void Register(RouteGroupBuilder parentGroup)
+    {
+        var group = parentGroup.MapGroup("/version");
+
+        group.MapGet("/", () => "v1");
+        group.MapGet("/test/dbconfig", (IOptions<OptixServeSettings> appSettings) =>
+        {
+            var dbType = appSettings.Value.Database?.Type;
+            var dbHost = appSettings.Value.Database?.Host;
+            return Results.Ok(new CommonErrorDto
+            {
+                Message = $"Set up {dbType} database on {dbHost}"
+            });
+        });
+    }
+}