post
https://example.com/profiles/investor//account/bind
Caller supplies an external network account they own. ownershipSignature is
required as proof-of-ownership and is verified by the LA. Async: returns 202 { cid }. If the
wallet is already bound to another investor — or to the same investor on the same
(org, asset) — completion reports WALLET_ALREADY_BOUND (409). A bad signature
reports WALLET_BAD_SIGNATURE (400).
