`receive_via_jit_channel()` with custom hash

[andrei-21]

To implement swap-in functionality with a JIT channel (i.e., swapping an on-chain payment to Lightning by opening a new channel), I need a method similar to receive_via_jit_channel() that supports a custom hash. The existing receive_for_hash() method is insufficient because it does not allow for skimmed fees.

Alternative Approaches:

Open a channel to LSP

An alternative to this functionality would be:

1. Receiving on-chain funds on the Lightning node.
2. Opening a channel to the LSP.

However, this approach has the following uncertainties:

• It is unclear whether the LSP will support zero-conf channels in this scenario.
• Without dual funding, the Lightning node will not obtain any inbound liquidity.

LSPS1

Request a channel from LSP. This approach requires the client to trust the LSP, which might be sometimes unacceptable (e.g. Breez).