Lets a brand-new user subscribe by paying in whatever token they
actually hold, converting it to the platform's settlement denomination
in the same PTB — no separate "acquire PUSD first" step. Composes a
swap with buildSubscribeTx's existing account-creation/deposit/subscribe
flow via the depositCoin seam, rather than requiring the caller to
already own a denomination coin the way coinsToUse does.
Lets a brand-new user subscribe by paying in whatever token they actually hold, converting it to the platform's settlement denomination in the same PTB — no separate "acquire PUSD first" step. Composes a swap with buildSubscribeTx's existing account-creation/deposit/subscribe flow via the
depositCoinseam, rather than requiring the caller to already own adenominationcoin the waycoinsToUsedoes.