Parsing of IPv6 addresses not enclosed in square brackets causes a
warning to be logged.
This is too strict, since the user can not influence IPv6 addresses
received over the network, but only those in their configuration.
Remove the warning from parsing, and instead carry a boolean to warn the
user later.
Teach the `rad sync` and `rad clone` commands to accept the
`--signed-refs-feature-level` option. This option configures that
fetch to use the minimum feature level provided when fetching from
other nodes. This overrides the value of
`node.fetch.signedReferences.featureLevel.minimum`, and should only be
used in scenarios where it is necessary to downgrade the security of a
fetch for backwards compatibility.
To achieve this, the `Handle::fetch` method introduces an optional
parameter for threading through the `FeatureLevel`.