* refactor: create log.Infof and log.Warnf * refactor: review DNS providers. - use one `http.Client` by provider instead of one client by request - use the same receiver name `d` for all `DNSProvider` - use `http.MethodXXX` * refactor: logger init.
* refactor: review DNS providers.
* Add 'dns-01' in CLI usage's solver list * Add Gandi Beta LiveDNS provider * gandiv5: rename provider and enhance error messages * gandiv5: clean old behavior comments * gandiv5: clean old behavior comments
