fix: don't strip slash from root href

Some servers require it (per #373 (comment)).

pystac_client/client.py

@@ -149,7 +149,6 @@ def open(
         Return:
             catalog : A :class:`Client` instance for this Catalog/API
         """
-        url = url.rstrip("/")
         client: Client = cls.from_file(
             url,
             headers=headers,
@@ -254,7 +253,7 @@ def get_collection(self, collection_id: str) -> Optional[Collection]:
             CollectionClient: A STAC Collection
         """
         if self._supports_collections() and self._stac_io:
-            url = f"{self.get_self_href()}/collections/{collection_id}"
+            url = self._get_href(f"collections/{collection_id}")
             collection = CollectionClient.from_dict(
                 self._stac_io.read_json(url),
                 root=self,
@@ -282,7 +281,7 @@ def get_collections(self) -> Iterator[Collection]:
         collection: Union[Collection, CollectionClient]
 
         if self._supports_collections() and self.get_self_href() is not None:
-            url = f"{self.get_self_href()}/collections"
+            url = self._get_href("collections")
             for page in self._stac_io.get_pages(url):  # type: ignore
                 if "collections" not in page:
                     raise APIError("Invalid response from /collections")
@@ -504,3 +503,12 @@ def get_search_link(self) -> Optional[pystac.Link]:
             ),
             None,
         )
+
+    def _get_href(self, path: str) -> str:
+        self_href = self.get_self_href()
+        if self_href is None:
+            return path
+        elif self_href.endswith("/"):
+            return f"{self_href}{path}"
+        else:
+            return f"{self_href}/{path}"

tests/test_client.py

@@ -146,6 +146,15 @@ def test_get_collections_single_slash(self, requests_mock: Mocker) -> None:
         assert len(history) == 2
         assert history[1].url == f"{root_url}collections"
 
+    def test_keep_trailing_slash_on_root(self, requests_mock: Mocker) -> None:
+        pc_root_text = read_data_file("planetary-computer-root.json")
+        root_url = "http://pystac-client.test/"
+        requests_mock.get(root_url, status_code=200, text=pc_root_text)
+        client = Client.open(root_url)
+        self_href = client.get_self_href()
+        assert self_href
+        assert self_href.endswith("/")
+
     def test_custom_request_parameters(self, requests_mock: Mocker) -> None:
         pc_root_text = read_data_file("planetary-computer-root.json")
         pc_collection_dict = read_data_file(