c.f. #8021
A lot of the code here is to change the `Completed 200 OK` logging to include the request URI so that we can drop the `Sending request...` log line.
Some notes:
1. We won't log retries, which may be confusing considering the time taken log line includes retries and sleeps.
2. The `_send_request_with_optional_trailing_slash` will always be logged *without* the forward slash, even if it succeeded only with the forward slash.
This refactors MatrixFederationAgent to move the SRV lookup into the
endpoint code, this has two benefits:
1. Its easier to retry different host/ports in the same way as
HostnameEndpoint.
2. We avoid SRV lookups if we have a free connection in the pool
If we have recently seen a valid well-known for a domain we want to
retry on (non-final) errors a few times, to handle temporary blips in
networking/etc.
It costs both us and the remote server for us to fetch the well known
for every single request we send, so we add a minimum cache period. This
is set to 5m so that we still honour the basic premise of "refetch
frequently".
Turns out that the library does a better job of parsing URIs than our
reinvented wheel. Who knew.
There are two things going on here. The first is that, unlike
parse_server_name, URI.fromBytes will strip off square brackets from IPv6
literals, which means that it is valid input to ClientTLSOptionsFactory and
HostnameEndpoint.
The second is that we stay in `bytes` throughout (except for the argument to
ClientTLSOptionsFactory), which avoids the weirdness of (sometimes) ending up
with idna-encoded values being held in `unicode` variables. TBH it probably
would have been ok but it made the tests fragile.
Patrick Cloke