PSF normalisation verification

In the weekly meeting we were wondering why the PSFs are not normalized in the .fits files... It looks like they are indeed normalised to "per area". Maybe it is worth to look at cell # 8 in https://github.com/shallmann/Analysis-galactic-sources-CTA-KM3NeT/blob/upgrade/gammapy2.0/Analysis/Plot_IRFs.ipynb

Note: this notebook is also already upgraded to gammapy 2; you can however find the same in the original notebooks by Tim