fix: allow booking the free part of a partly booked day

src/Booking/SpotState.php

@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Booking;
+
+/**
+ * How one resource looks on the floor plan, for the day and span the board is showing.
+ *
+ * PARTLY exists because of a real bug: with only "free" and "taken", a desk booked 09:00-13:00
+ * looked identical to one booked all day on an all-day board, and was equally unclickable -- so
+ * nobody could book the afternoon without first knowing to narrow the span by hand.
+ */
+enum SpotState
+{
+    case FREE;
+    case PARTLY;
+    case TAKEN;
+    case MINE;
+
+    public function isBookable(): bool
+    {
+        return self::FREE === $this || self::PARTLY === $this;
+    }
+}