branch order assigned by setup river needs improvement at bifurcation

[xldeltares]

Kind of request

Changing existing functionality

Enhancement Description

For now, when we use setup_river function, a branch order = 1 is by default applied, so that river crossection are interpolated. this works well in simple river cases but when river network becomes more complex, this is not correct and will give an error in the model at bifurcation locations. we should assign branch order in a more smart way.

Use case

No response

Additional Context

After discussion we decided to use branch order -1. Only when an user specifies the order, it will overwrite the -1. You need knowledge about the system to do this properly.

[xldeltares]

closed with #38