std_options.http_connection_pool_size removed in favor of
```
client.connection_pool.resize(client.allocator, size);
```
std_options.http_disable_tls will remove all https capability from
std.http when true. Any https request will error with
`error.TlsInitializationFailed`.
Solves #17051.
adds connectTunnel to form a HTTP CONNECT tunnel to the desired host.
Primarily implemented for proxies, but like connectUnix may be called by
any user.
adds loadDefaultProxies to load proxy information from common
environment variables (http_proxy, HTTP_PROXY, https_proxy, HTTPS_PROXY,
all_proxy, ALL_PROXY).
- no_proxy and NO_PROXY are currently unsupported.
splits proxy into http_proxy and https_proxy, adds headers field for
arbitrary headers to each proxy.
Addresses #17015 by introducing a new startWithOptions. The only option is currently is a flag
to use the provided URI as is, without modification when passed to the server. Normally, this
is not needed nor desired. However, some REST APIs may have requirements that cannot be satisfied
with the default handling.
Make to avoid releasing request's connection twice.
Change the `Request.connection` field optional. This field is null while the connection is released.
Fixes#15965
