[BUG] Layover countries marked visited when flights are imported from AirTrail

Pre-flight checklist

• I have searched existing issues and this bug has not been reported yet
• I am running the latest available version of TREK
• I have read the Troubleshooting guide and my issue is not covered there

TREK version

3.3.0

Describe the bug

When importing flights from AirTrail they cannot be connected to multi-leg flights (see #1431). So stops cannot be declared as layover. As a consequence these countries get saved as visited which is not correct (see #1366 and #1486).

Steps to reproduce

1. Import flights from AirTrail with layover
2. Country with layover gets saved as visited in Atlas and can’t be removed.

Expected behavior

Flights from AirTrail should be able to get joined so layover countries don’t count as visited.

Deployment method

Docker Compose

Host OS

No response

Accessing TREK from

Desktop browser

Browser (if applicable)

No response

Relevant logs or error output

Screenshots

No response

Additional context

No response