Fix crash on access point presence events

[abeltrano]

Type

• Bug fix
• Feature addition
• Feature update
• Documentation
• Build Infrastructure

Side Effects

• Breaking change
• Non-functional change

Goals

• Ensure access points that arrive/depart after starting netremote-server are handled correctly and do not cause a crash.
• Fix Bug: New AP arrival causes crash in netremote-server #125

Technical Details

• Re-use Nl80211Interface parsing code for decoding nl80211 event info on presence change events.
• Pass AccessPointCreateArgsLinux args when constructing access points in response to presence change events (this is the bug fix).
• Emit info-level log messages on access point presence events.
• Make Nl80211Interface suitable for use in unique containers.
• Replace use of std::unordered_map of utility structure with std::unordered_set<Nl80211Interface> for the "seen" cache.

Test Results

• All unit tests pass.
• Toggled the hostapd service for an interface while netremote-server was running and validated log output was expected:

Netremote server starting
Netremote server started listening on 0.0.0.0:5047
Handling netlink socket read availabilty
Received netlink message callback
Received NL80211_CMD_SET_INTERFACE nl80211 command message
Invoking access point presence event callback with event args 'interface=wls1, presence=Arrived'
Access Point Discovery Event: Interface wls1 Arrived
Processed netlink message with result 0
Successfully processed netlink messages
Handling netlink socket read availabilty
Received netlink message callback
Received NL80211_CMD_SET_INTERFACE nl80211 command message
Invoking access point presence event callback with event args 'interface=wls1, presence=Departed'
Access Point Discovery Event: Interface wls1 Departed
Processed netlink message with result 0
Successfully processed netlink messages
Handling netlink socket read availabilty
Received netlink message callback
Received NL80211_CMD_SET_INTERFACE nl80211 command message
Invoking access point presence event callback with event args 'interface=wls1, presence=Arrived'
Access Point Discovery Event: Interface wls1 Arrived
Processed netlink message with result 0
Successfully processed netlink messages

Reviewer Focus

• None

Future Work

• None

Checklist

• Build target all compiles cleanly.
• clang-format and clang-tidy deltas produced no new output.
• Newly added functions include doxygen-style comment block.