feat(schema): add budget_prev attributes
this attribute will describe:
- the total budget, that will be used for trajectory computations
related: https://forge.extranet.logilab.fr/logilab/shingouz/-/issues/44
Edited by Simon Chabot
this attribute will describe:
related: https://forge.extranet.logilab.fr/logilab/shingouz/-/issues/44