Derive mode from DSN function

- Add headers in all files
- Minor field name changes

tests/unit/ConfigurationTest.php

@@ -1,4 +1,10 @@
-<?php declare(strict_types=1);
+<?php
+/**
+ * @author Daniel J. Summers <daniel@bitbadger.solutions>
+ * @license MIT
+ */
+
+declare(strict_types=1);
 
 namespace Test\Unit;
 
@@ -46,7 +52,7 @@ class ConfigurationTest extends TestCase
     public function testDbConnFailsWhenNoDSNSpecified(): void
     {
         $this->expectException(DocumentException::class);
-        Configuration::$pdoDSN = '';
+        Configuration::useDSN('');
         Configuration::dbConn();
     }
 }