alpha2 (#2)

- Change multiple field matching to enum
- Implement auto-generated IDs

Reviewed-on: #2

src/FieldMatch.php

@@ -0,0 +1,28 @@
+<?php declare(strict_types=1);
+
+namespace BitBadger\PDODocument;
+
+/**
+ * How multiple fields should be matched
+ */
+enum FieldMatch
+{
+    /** Match all provided fields (`AND`) */
+    case All;
+
+    /** Match any provided fields (`OR`) */
+    case Any;
+
+    /**
+     * Get the SQL keyword for this enumeration value
+     *
+     * @return string The SQL keyword for this enumeration value
+     */
+    public function toString(): string
+    {
+        return match ($this) {
+            FieldMatch::All => 'AND',
+            FieldMatch::Any => 'OR'
+        };
+    }
+}