user_create_margin
Init the PDA. Authority = signer.
user_deposit_collateral(amount)
init_if_needed vault ATA. Measured transfer in. Register the asset index on first use.
user_withdraw_collateral(amount, min_health_factor_wad)
Full-set health after the withdrawal. Must exceed min_health_factor_wad and the 1.1 threshold when debt remains.