consider reserved bandwith for path calculation

[ggrammel]

Is your feature request related to a problem? Please describe.
operators sometimes want to set aside frequency ranges for specific purposes this include:

• guard bands (not planned to be used)
• some special purpose wavelength (e.g. synchronisation, special communications, ..)
• to group wavelength of a certain characteristic (e.g. DQPSK and QAM16 or power levels)

Describe the solution you'd like
have a suitable way to describe those frequency ranges and their power spectral density. It would also be nice to be able to formulate rules to automatically sort demands in the targeted ranges for path computation.

Describe alternatives you've considered
not really aware of what else can be done

Additional context
It is obvious that "opaque wavelength" i.e. wavelength with unknown characteristics are hard to cover. However it would make sense to provide a parametrizable penalties. Note: it is not required to be able to route such wavelength or to calculate feasibility for those. These wavelength are typically few and could be considered in a coarse way.