We normally check errors for all operations. But for some cleanup calls, eg
"defer file.Close()", we didn't. Now we also check and log most of those.
Partially because those errors can point to some mishandling or unexpected code
paths (eg file unexpected already closed). And in part to make it easier to use
"errcheck" to find the real missing error checks, there is too much noise now.
The log.Check function can now be used unconditionally for checking and logging
about errors. It adjusts the log level if the error is caused by a network
connection being closed, or a context is canceled or its deadline reached, or a
socket deadline is reached.
we use 6 weeks as the cutoff, but this is fuzzy, and will vary by mail
server/service provider.
we check the domain age using RDAP, the replacement for whois. it is a
relatively simple protocol, with HTTP/JSON requests. we fetch the
"registration"-related events to look for a date of registration.
RDAP is not available for all country-level TLDs, but is for most (all?) ICANN
global top level domains. some random cctlds i noticed without rdap: .sh, .au,
.io.
the rdap implementation is very basic, only parsing the fields we need. we
don't yet cache the dns registry bootstrap file from iana. we should once we
use this functionality from the web interface, with more calls.
