At the moment a very limited amount of options are supported for static_routes defenition, which might be a limiting factor in some more complex solutions. It is proposed to let operators define `static_routes` with parameters that are available in systemd-networkd [1] directly, which should provide required flexbility and not require us additional maintenance and regular updates of the code. [1] https://www.freedesktop.org/software/systemd/man/latest/systemd.network.html#%5BRoute%5D%20Section%20Options Change-Id: I71f81cb497ae8eeb0fab2bc6f9f5eae120d10775