feat: save LDK static channel backups to disk

[rolznz]

Fixes https://github.com/getAlby/hub/issues/646

This is only done for LDK so I decided to add this logic directly in the LDK implementation.

I don't think we take responsibility for LND - that should be done by LND itself?

$ cat .data/ldk/static_channel_backups/2024-09-21T13\:57\:48+07\:00.json

[{"channel_id":"e3bed0e8ae812f5712c02e6b0fee261f04881d5034db446414eec28d643d0f0e","node_id":"02419a12598b7bfd2ce33769ad850a3a0d3ae0b9e7a5493780ac2b4ac682090bd3","peer_id":"032ae843e4d7d177f151d021ac8044b0636ec72b1ce3ffcde5c04748db2517ab03","channel_size":1000000,"funding_tx_id":"0e0f3d648dc2ee146444db34501d88041f26ee0f6b2ec012572f81aee8d0bee3","funding_tx_vout":0},{"channel_id":"1d05be99c206e8ea8d5a18cb39568b42d015b9b5e99da3d783403214227a10da","node_id":"02419a12598b7bfd2ce33769ad850a3a0d3ae0b9e7a5493780ac2b4ac682090bd3","peer_id":"02465ed5be53d04fde66c9418ff14a5f2267723810176c9212b722e542dc1afb1b","channel_size":250000,"funding_tx_id":"db107a2214324083d7a39de9b5b915d0428b5639cb185a8deae806c299be051d","funding_tx_vout":1},{"channel_id":"5b5bbf63e335cbbfb4e2eb734626cd8590537e0b402e0d1e34531fe12f7496b8","node_id":"02419a12598b7bfd2ce33769ad850a3a0d3ae0b9e7a5493780ac2b4ac682090bd3","peer_id":"03e30fda71887a916ef5548a4d02b06fe04aaa1a8de9e24134ce7f139cf79d7579","channel_size":1000000,"funding_tx_id":"b896742fe11f53341e0d2e400b7e539085cd264673ebe2b4bfcb35e363bf5b5b","funding_tx_vout":0},{"channel_id":"c48d500706ae0c907db45440812bfc85a48d3630ad6bf41544280ca2d294dc0a","node_id":"02419a12598b7bfd2ce33769ad850a3a0d3ae0b9e7a5493780ac2b4ac682090bd3","peer_id":"03e30fda71887a916ef5548a4d02b06fe04aaa1a8de9e24134ce7f139cf79d7579","channel_size":1000000,"funding_tx_id":"0adc94d2a20c284415f46bad30368da485fc2b814054b47d900cae0607508dc4","funding_tx_vout":0},{"channel_id":"8e2097f61a647f3d1a1ef9a17452e7f11982891eb1fd198ce101ab4bcbbe05fa","node_id":"02419a12598b7bfd2ce33769ad850a3a0d3ae0b9e7a5493780ac2b4ac682090bd3","peer_id":"03e30fda71887a916ef5548a4d02b06fe04aaa1a8de9e24134ce7f139cf79d7579","channel_size":1000000,"funding_tx_id":"fa05becb4bab01e18c19fdb11e898219f1e75274a1f91e1a3d7f641af697208e","funding_tx_vout":0},{"channel_id":"2f9b0145c53632ae5a4cff2b6d57f50390ff3d355e96b9c99634aa9e4611dc6a","node_id":"02419a12598b7bfd2ce33769ad850a3a0d3ae0b9e7a5493780ac2b4ac682090bd3","peer_id":"03e30fda71887a916ef5548a4d02b06fe04aaa1a8de9e24134ce7f139cf79d7579","channel_size":150000,"funding_tx_id":"6adc11469eaa3496c9b9965e353dff9003f5576d2bff4c5aae3236c545019b2f","funding_tx_vout":0}]

[bumi]

good idea to handle it there! 👍