feat: add support for pagination

lektor_groupby/pagination.py

@@ -0,0 +1,14 @@
+from lektor import datamodel
+from typing import TYPE_CHECKING, Any
+if TYPE_CHECKING:
+    from lektor.db import Record
+
+
+class PaginationConfig(datamodel.PaginationConfig):
+    # because original method does not work for virtual sources.
+    @staticmethod
+    def get_record_for_page(source: 'Record', page_num: int) -> Any:
+        for_page = getattr(source, '__for_page__', None)
+        if callable(for_page):
+            return for_page(page_num)
+        return datamodel.PaginationConfig.get_record_for_page(source, page_num)