dont break on app startup when pagination extension is not included (#444)

* dont break on app startup when pagination extension is not included

* update changelog

* better variable names

Author: geospatial-jeff

CHANGES.md

@@ -43,6 +43,7 @@
   from the request body, if present, and falls back to using the path parameter if no `"collection"` property is found in the body
   ([#425](https://github.com/stac-utils/stac-fastapi/pull/425))
 * PGStac Backend Transactions endpoints return added Item/Collection instead of Item/Collection from request ([#424](https://github.com/stac-utils/stac-fastapi/pull/424))
+* Application no longer breaks on startup when pagination extension is not included ([#444](https://github.com/stac-utils/stac-fastapi/pull/444))
 
 ## [2.3.0]
 

stac_fastapi/api/stac_fastapi/api/app.py

@@ -275,11 +275,15 @@ def register_get_item_collection(self):
         Returns:
             None
         """
-        get_pagination_model = self.get_extension(self.pagination_extension).GET
+        pagination_extension = self.get_extension(self.pagination_extension)
+        if pagination_extension is not None:
+            mixins = [pagination_extension.GET]
+        else:
+            mixins = None
         request_model = create_request_model(
             "ItemCollectionURI",
             base_model=ItemCollectionUri,
-            mixins=[get_pagination_model],
+            mixins=mixins,
         )
         self.router.add_api_route(
             name="Get ItemCollection",