Should not allow a route with the same departure and arrival nodes

[kaligrafy]

It happens on some networks with sparse lines and paths

[greenscientist]

@kaligrafy Thinking of a few details here: Do we want to skip if there's exactly just one departure and arrival node and they are the same ? If there's multiple, do they need to be exactly the same set? Or if they have one node in common, we also skip it? What should be the error message? (See the API doc.)

[kaligrafy]

We should return an error message if only one origin and arrival nodes and they are the same. Like "Origin and destination nodes are the same"

[kaligrafy]

For the case with multiple orign and destianation nodes, I don't know, transit routing could still be possible, but highly unlikey to be used, except with very large maximum access/egress walking travel times.

[greenscientist]

We should return an error message if only one origin and arrival nodes and they are the same. Like "Origin and destination nodes are the same"

Ok, should be easy to add the check for this case.