Use custom login client when SSL_CERT_FILE is set
If SSL_CERT_FILE env var is set, use this file as a source of root certificates (a new reqwest client is created for that). This is useful for HTTPS proxies or servers with custom CAs in Flatpaks, where users can't overwrite default CA bundle location.
Fixes #425 (closed), #695
Edited by Vadim Rutkovsky