No File.refresh() during File.append_block (#585)

The current code, upon appending a `Block` to a `File`, immediately
calls `File.refresh()` to update the state of the `File` object. This PR
adds the newly created `Block` directly to the `File` without making a
second API call.

The risk / downside to this is that any blocks that were created on the
File in between are now not loaded as part of this call.

src/steamship/data/file.py

@@ -360,7 +360,15 @@ def append_block(
             mime_type=mime_type,
             public_data=public_data,
         )
-        self.refresh()
+        if (
+            self.blocks is not None
+            and len(self.blocks) > 0
+            and block.index_in_file == self.blocks[-1].index_in_file + 1
+        ):
+            self.blocks.append(block)
+        else:
+            self.refresh()
+
         return block
 
     def set_public_data(self, public_data: bool):

tests/steamship_tests/data/test_block.py

@@ -174,6 +174,9 @@ def test_append_is_present(client: Steamship):
     file.refresh()
     assert len(file.blocks) == 2
 
+    file.append_block(text="third")
+    assert len(file.blocks) == 3
+
     my_file = File.create(client, handle="my_file", content="")
     assert len(my_file.blocks) == 0
     my_file.append_block(text="first")