the DNS backends require many different params, it's just easier to
pass them all together and have backends do whatever.
For example, route53 API requires the fqdn. Some other backends require just the
"part" to insert.
* location - location in the database (where app is installed)
* zoneName - the dns zone name
* domain - domain in the database (where apps are installed into)
* name/getName() - this returns the name to insert in the DNS based on zoneName/location
* fqdn - the fully resolved location in zoneName
verifyDnsConfig also takes a domain object even if it's not in db just so that we can
test even existing domain objects, if required. The IP param is removed since it's not
required.
for caas, we also don't need the fqdn hack in dnsConfig anymore
DNS records can now be a A record or a CNAME record. All we care
about is them resolving to the public IP of the server somehow.
The main reason for this change is that altDomain is migrated into
domains table and the DNS propagation checks have to work after that.
(previously, the 'altDomain' was a signal for a CNAME check which now
cannot be done post-migration).
In the future, we can make this more sophisticated to instead maybe
do a well-known URI query. That way it will work even if there is
some proxy like Cloudflare in the middle.
Fixes#503
Girish Ramakrishnan