Review slip-road handlers

[MoKob]

Scenario 1

primary via primary_link onto secondary.

osrm

This feels like a primary candidate for a sliproad.

• investigate handler that discards it
• adjust if possible
• evaluate other affected locations

Scenario 2

tertiary via tertiary_link onto second residential.

osrm

Looks very similar to scenario 3, only down two road categories. Actions remain the same:

• investigate handler that discards it
• adjust if possible
• evaluate other affected locations

Scenario 3

residential_road via residential_road onto residential_road

osrm

This one is tricky, due to no link class. Given the matching names and the short segment, we might be able to detect these.

• investigate handler that discards it
• adjust if possible
• evaluate other affected locations

Scenario 4

motorway_link via motorway_link onto primary

osrm

This might be influenced with us treating motorways differently than normal roads.

• investigate handler that discards it
• adjust if possible
• evaluate other affected locations

[oxidase]

@MoKob in the 4th scenario sliproad handler discards the sliproad candidate at

osrm-backend/src/extractor/guidance/sliproad_handler.cpp

Line 713 in e512431

return false;

because first road is also a motorway_link

[oxidase]

All four cases are merged as separate PRs