Add helper logic around the server_url arg

[Coniferish]

Same issue as was opened in the unstructured-python-client repo: Unstructured-IO/unstructured-python-client#30

• If a path is included with the custom url, strip the path rather than return a 404
• If the url uses http or has no protocol, prefix with https instead

This will be custom logic on top of the autogenerated code. Speakeasy will provide hooks to do this soon, but for now we should establish a pattern, and maintain this code whenever a pr is regenerated.

See solution here: Unstructured-IO/unstructured-python-client#32