Fix URL when bucket is contained in endpoint

[SplittyDev]

TL;DR

This fixes a bug¹ where the URL is constructed incorrectly in the case that the S3 host/endpoint already contains the bucket name in the URL and path-style URLs are enabled.

Example

Cloudflare R2 storage specifies an URL such as this:
https://12345foo.r2.cloudflarestorage.com/my-bucket

Since the bucket is specified in the URL given by Cloudflare, but also added at the end of the endpoint, this results in requests failing with 400 Bad Request.

What we did

We fixed this simply by checking whether the host ends in /{bucket_name}, and skipping inclusion of the bucket at the end if that's the case. We also added a test case to make sure the behavior works correctly and doesn't regress.

Footnotes

1. I'm actually not 100% sure this is really a bug, but this fix makes life easier, especially for R2 users. ↩