Massively simplify API binding logic

Changes the API internals to use normal Laravel binding which automatically supports nested-models and can determine their relationships. This removes a lot of confusingly complex internal logic and replaces it with standard Laravel code.

This also removes a deprecated "getModel" method and fully replaces it with a "parameter" method that does stricter type-checking.

app/Models/Task.php

@@ -105,6 +105,14 @@ class Task extends Model
         'continue_on_failure' => 'boolean',
     ];
 
+    /**
+     * {@inheritDoc}
+     */
+    public function getRouteKeyName(): string
+    {
+        return $this->getKeyName();
+    }
+
     /**
      * Return a hashid encoded string to represent the ID of the task.
      *