[feature]: BumpFee: return raw tx hex on success

[kaloudis]

Is your feature request related to a problem? Please describe.
Currently the bumpfee command will just return an empty object on success.

Describe the solution you'd like
It would be nice to receive the raw transaction hex to manually broadcast in cases in which the transaction does not propagate

[yyforyongyu]

There's this PR #8426 that can be used for reference when implementing this.

[mohamedawnallah]

Hey @kaloudis @yyforyongyu I'd like to work on this issue. Before the actual implementation of this issue, I've put down one question and also how I'm gonna tackle this issue. Thanks for your help! 🙏

Questions

How to convert Outpoint.TxidStr to raw hex string so that we could integrate it in BumpFee method in walletkit_server.go?

How I am gonna tackle this issue

1. Update the walletkit.proto file to include include_raw_tx flag in BumpFeeRequest message and tx_hex in BumpFeeResponse.
2. Compile the proto files and update the swagger api documentation using make rpc command.
3. Add the include_raw_tx boolean flag and update BumpFeeRequest with IncludeRawTx in walletrpc_active.go.
4. Handle the case where in.IncludeRawTx is true and bumpfee succeeded by converting in.Outpoint.TxidStr to a raw hex string (the main question) and assign it to TxHex field in BumpFeeResponse struct in walletkit_server.go.
5. Test TxHex field is created as expected in BumpFeeResponse struct when the IncludeRawTx flag option is true in itest/lnd_onchain_test.go.
6. Test it locally by running make install tags="walletrpc" and lncli wallet bumpfee --sat_per_vbyte 150 --include_raw_tx <unconfirmed_funding_tx_id>:<index> and check the tx_hex is included in the BumpFeeResponse.
7. Run make check to check against any regressions (if any).
8. Finally update the release-notes.

[mohamedawnallah]

Thanks figured it out while working on issue #8515 I just needed more time to get hands-on with the codebase.

How to convert Outpoint.TxidStr to raw hex string so that we could integrate it in BumpFee method in walletkit_server.go?