feat: generate draft assignments from a staffing matrix

src/Model/StaffingCandidate.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace App\Model;
+
+use App\Entity\Destination;
+use App\Entity\StaffingRule;
+
+/**
+ * A travel date the staffing matrix applies to, with what would be created for it.
+ */
+final readonly class StaffingCandidate
+{
+    /**
+     * @param list<PlannedAssignment> $planned
+     */
+    public function __construct(
+        public Destination $destination,
+        public StaffingRule $rule,
+        public array $planned,
+        /** It has had an assignment before, so it is never generated again. */
+        public bool $skipped,
+    ) {
+    }
+}