[RM-7982] [linemodel] better condition to assess minimal fraction of a line to be measured

Created on 2023-03-28 10:57:47 by Didier Vibert. % Done: 0

The current condition to include a line in the model, is to asses the fact that at least 30% of half the support (-4sigma, +4sigma) is visible on the extremities of the lambda range.

1. it only consider the spectral range, and not the eventual holes inside du to masked out samples
2. the 30% is on the border of the line support, meaning the center of the line may be 60% away of the border.

we should may be ask that at least one sample is close enough to the center ? and require a minimal number of samples and/or a minimal fraction of support covered by the observed samples ?