feat: add CLN backend

[daywalker90]

Hi alby team :)

I know the CLN API pretty well by now and i only had to get into go and typescript (it was fun) to get this one done. if err != nil btw.

This is barely tested. I'm pretty sure some functions were never called during my time clicking around in the web frontend. Please let me know how to test this in a good way.

Also please let me know what else i missed or got wrong.

While CLN ships with gRPC support, CLN doesn't have native support for hold invoices so i added optional configs for boltz's hold plugin.

Not tested but i think the minimum version for CLN is v24.11 and hold v0.3.3

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[rolznz]

@daywalker90 awesome, thanks for the PR! what's the best way to test this? can I use Polar?

[daywalker90]

Never used Polar but they list CLN aswell on their website. The configs grpc-host and grpc-port have defaults, but for the hold plugin you need to set the configs.

Myself i have CLN installed from compiling the source and then you can run a script from the CLN repo like this:

source contrib/startup_regtest.sh

which gives these commands:

Useful commands:
  start_ln 3: start three nodes, l1, l2, l3
  connect 1 2: connect l1 and l2
  fund_nodes: connect all nodes with channels, in a row
  stop_ln: shutdown
  destroy_ln: remove ln directories

You can install a plugin like the hold plugin by copying/linking it in a newly created directory plugins inside the nodes lightning-dir or by adding it to the config like this: plugin=/path/to/plugin