Turn __in filter lists into comma-separated strings (#227)

For `__in` filters, the Paperless NGX API expects a comma-separated
string of IDs, not a list (see
paperless-ngx/paperless-ngx#6996). This patch
turns a list into such a string for `__in` filters.

Closes: #226

Signed-off-by: martin f. krafft <[email protected]>

src/pypaperless/models/mixins/helpers/iterable.py

@@ -91,11 +91,25 @@ def pages(
 
         """
         params = getattr(self, "_aiter_filters", None) or {}
+
+        for param in params:
+            if param.endswith("__in"):
+                value = params[param]
+                try:
+                    value.extend([])  # throw AttributeError if not a list
+                    params[param] = ",".join(map(str, value))
+
+                except AttributeError:
+                    # value is not a list, don't modify
+                    continue
+
         params.setdefault("page", page)
         params.setdefault("page_size", page_size)
 
         # set requesting full permissions
         if getattr(self, "_request_full_perms", False):
             params.update({"full_perms": "true"})
 
-        return PageGenerator(self._api, self._api_path, self._resource_cls, params=params)
+        return PageGenerator(
+            self._api, self._api_path, self._resource_cls, params=params
+        )