Calculate the number of file descriptors that are needed during
execution based on the configuration file, with a hard floor
of 1024, adjusting the limit if possible. Refuse to run if enough
fds are not available.
Additionally, allow administrators to limit the number of incoming
connections a configured port will accept. By default no limit is
imposed.
This is designed for use by proxies in front of rippled. Configured IPs
can forward identifying user data in HTTP headers, including
user name and origin IP. If the user name exists, then resource limits
are lifted for that session. However, administrative commands are still
reserved only for administrative sessions.