Add https:// to front of domain argument if it's not a URL

The "domain" argument to the 2FAS API isn't actually expecting a
domain, it's expecting a URL (see
twofas/2fas-server#6).

Arguably it would be better to rename the "--domain" argument in this
script to "--url" for clarity, but absent that, at the very least we
should check if the user specifies a domain instead of a URL—since
that's what the parameter is called, it's an easy mistake to make!—and
if so, then add "https://" to the beginning of it so that we're
passing the 2FAS server something it expects.

Fixes dspitzer#1.

twofas_cli/twofas_cli.py

@@ -62,7 +62,9 @@ def get(domain: str, identifier: str, api_base_url: str, ws_base_url: str):
     if identifier:
         domain = re.sub(r'[^a-zA-Z0-9 -.]', '', identifier.strip()).lower()
         domain = 'https://' + domain.replace(' ', '.') + '.2fa.invalid'
-
+    elif not re.match(r'https?://', domain):
+        domain = 'https://' + domain
+
     api = TwoFasApi(api_base_url, ws_base_url)
     extension_id = get_extension_id()
     response = api.request2_fa_token(extension_id, domain)