+ /// Add local signature for LocalCommitmentTransaction, do nothing if signature is already
+ /// present
+ ///
+ /// Funding key is your key included in the 2-2 funding_outpoint lock. Should be provided
+ /// by your ChannelKeys.
+ /// Funding redeemscript is script locking funding_outpoint. This is the mutlsig script
+ /// between your own funding key and your counterparty's. Currently, this is provided in
+ /// ChannelKeys::sign_local_commitment() calls directly.
+ /// Channel value is amount locked in funding_outpoint.