SignRawTransactionWithKey

[galileo-pkm]

More or less a copy of SignRawTransactionWithWallet method that implements
the signrawtransactionwithkey bitcoind RPC.

[coveralls]

Pull Request Test Coverage Report for Build 3039397202

• 9 of 74 (12.16%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-3.0%) to 52.137%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
rpcclient/rawtransactions.go	0	65	0.0%

Files with Coverage Reduction	New Missed Lines	%
btcutil/gcs/gcs.go	1	81.25%

Totals
Change from base Build 2836573928:	-3.0%
Covered Lines:	23312
Relevant Lines:	44713

---

💛 - Coveralls

[galileo-pkm]

Can someone please review this?

[DhananjayPurohit]

Thanks @galileo-pkm, I also need this function in a project. It would be great if it could be merged (as maintaining another version of this package in a fork can be tedious). I would love to take this PR ahead along with @galileo-pkm if it needs any other work. @guggero @Roasbeef

[guggero]

@DhananjayPurohit you're welcome to review and test this PR to help move it along.

@galileo-pkm I know this isn't consistently done throughout all code in btcd yet, but we're trying to use the same formatting and code guidelines as we do in lnd, at least in new code: https://github.com/lightningnetwork/lnd/blob/master/docs/code_formatting_rules.md

[galileo-pkm]

I'm recovering from surgery and won't be able to work for quite some time, if anyone else wants to take over feel free to do so.

@galileo-pkm I know this isn't consistently done throughout all code in btcd yet, but we're trying to use the same formatting and code guidelines as we do in lnd, at least in new code: https://github.com/lightningnetwork/lnd/blob/master/docs/code_formatting_rules.md