feat: implemented smtp service;

feat: implemented registration emails;
fix: config variables for password length used the same env variable;
refactor: all available config variables added to docker-compose.yml

backend/internal/services/setup.go

@@ -23,6 +23,7 @@ import (
 
 var Module = fx.Module("services",
     fx.Provide(
+			NewSmtpService,
 			NewAuthService,
     ),
 )