Add some more "handler" docs

app handler, batch handlers, native batch types, people handler

docs/data/batch/native/delproduct.rst

@@ -0,0 +1,22 @@
+
+Delete Product Batch
+====================
+
+**Batch Type Key:** ``delproduct``
+
+**Purpose:** Delete products from the system.
+
+**Default Handler:** :class:`~rattail:rattail.batch.delproduct.DeleteProductBatchHandler`
+
+Data for this batch may come from spreadsheet file or grid query, etc.
+
+It should try to catch potential issues which might arise should the
+products actually be deleted, for instance if a given item has pending
+customer orders.
+
+It also should try to highlight items which have seen recent movement,
+to help avoid removing items which are more active than you thought
+etc.
+
+Ultimately executing this batch will just update Rattail by default;
+you may want a custom handler to update your POS system instead.