Refactor `mullvad-relay-selector`

Implement a system built on 'queries' for selecting appropriate relays.
A query is a set of constraints which dictates which relay(s) that *can*
be chosen by the relay selector.

The user's settings can naturally be expressed as a query. The semantics
of merging two queries in a way that always prefer user settings is
defined by the new `Intersection` trait.

Split `mullvad-relay-selector` into several modules:

- `query.rs`: Definition of a query on different types of relays. This
module is integral to the new API of `mullvad-relay-selector`
- `matcher.rs`: Logic for filtering out candidate relays based on a
query.
- `detailer.rs`: Logic for deriving connection details for the selected
relay.
- `tests/`: Integration tests for the new relay selector. These tests
only use the public APIs of `RelaySelector` and make sure that the
output matches the expected output in different scenarios.

1 files changed, 5 insertions, 8 deletions

diff --git a/mullvad-daemon/src/settings/mod.rs b/mullvad-daemon/src/settings/mod.rs
index abd6ea2e0a..b1d9c2b8e6 100644
--- a/mullvad-daemon/src/settings/mod.rs
+++ b/mullvad-daemon/src/settings/mod.rs
@@ -376,16 +376,13 @@ impl<'a> Display for SettingsSummary<'a> {
             write!(f, ", wg ip version: {ip_version}")?;
         }
 
-        let multihop = matches!(
-            relay_settings,
+        let multihop = match relay_settings {
             RelaySettings::Normal(RelayConstraints {
-                wireguard_constraints: WireguardConstraints {
-                    use_multihop: true,
-                    ..
-                },
+                wireguard_constraints,
                 ..
-            })
-        );
+            }) => wireguard_constraints.multihop(),
+            _ => false,
+        };
 
         write!(
             f,