Add project files

StalwartSimpleLoginMiddleware/Utilities/ConnectionHelper.cs

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+using Npgsql;
+
+namespace StalwartSimpleLoginMiddleware.Utilities;
+
+public static class ConnectionHelper
+{
+    public static string GetPostgresConnectionString(string url)
+    {
+        var uri = new Uri(url);
+        var userInfo = uri.UserInfo.Split(':');
+        var builder = new NpgsqlConnectionStringBuilder
+        {
+            Host = uri.Host,
+            Port = uri.Port,
+            Database = uri.AbsolutePath.Trim('/'),
+            Username = userInfo[0],
+            Password = userInfo[1],
+            SslMode = SslMode.Prefer
+        };
+        return builder.ToString();
+    }
+}