Feature request: Handle templated and concatenated string in route paths

[AlbRoehm]

As mentioned in the slack message it would be great to use const val strings, concatednated or templated strings for paths.

I tried to extend the FirFunctionCall.extractArguments() in ExpressionVisitorK2.kt which from my shallow understanding is doing this job but after a few hours i was not able to come up a pr. Somehow i was unable to extract the needed values out of the FirStringConcatenationCall and FirPropertyAccessExpression. I will try to follow your pr in case you can take this issue up to get some more understanding about the plugin world.