Auto SSL for Tenant Domains for a SaaS Service

caddy.conf

# for checking if it belongs ot our domain list
{
	  email myemail@example.test
    on_demand_tls {
        ask     https://api.example.test/check-domain
        interval 2m
        burst    5
    }
}

# for specific domains
app.example.test {
	reverse_proxy xxx.xxx.xxx.xxx:4000
}

# for any domains
https:// {
	tls {
		on_demand
	}

	handle {
		reverse_proxy xxx.xxx.xxx.xxx:5000
	}
}