In local setups, such as a Minio [1] instance in a Docker container,
the protocol may not always be HTTPS (like for public production
endpoints), but instead just plain HTTP.
To support this use-case, the user can specify a protocol at the
beginning of the custom endpoint URI (either http:// or https://).
To maintain backwards compatibility, the protocol defaults to HTTPS.
The patch also includes a test case to assert this behavior.
[1] https://hub.docker.com/r/minio/minio