URL scheme config auto-setting may cause errors in certain deployments

[brassy-endomorph]

Describe the bug

We set the URL scheme to https if the SERVER_NAME config is set. This may cause bugs with .onion addresses or IP addresses where users land on http:// and then every link that's generated is https://

hushline/hushline/__init__.py

Lines 65 to 67 in ce44578

	# Handle the tips domain for profile verification
	app.config["SERVER_NAME"] = os.getenv("SERVER_NAME")
	app.config["PREFERRED_URL_SCHEME"] = "https" if os.getenv("SERVER_NAME") is not None else "http"

Suggested Fix

May this an independently configurable variable.