after some more thought:
* If app moves to another location, user has to remember to move all this config
* It's not really associated with an app. It's to do with the domain info
* We can put some hints in the UI if app is missing.
part of #703
* app certs set by user are always preferred
* If fallback, choose fallback certs. ignore others
* If LE, try to pick LE certs. Otherwise, provider fallback.
Fixes#724
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
when certs change, we have to call into nginx anyway. since they
go hand in hand, just merge those files. modern reverse proxies
do this job integrated already.
