Add initial implementation of API, database, and user management components.

MikrocopApi/Exceptions/ConflictException.cs

@@ -0,0 +1,11 @@
+namespace MikrocopApi.Exceptions;
+
+public sealed class ConflictException : AppException
+{
+    public ConflictException(string message) : base(message)
+    {
+    }
+
+    public override int StatusCode => StatusCodes.Status409Conflict;
+    public override string Title => "Conflict";
+}