Add get invoice feature

[Dolu89]

[louneskmt]

We should change "get" to "decode" as "get" might mean we are querying an existing invoice in the node database.

Also, FYI the decodepay method isn't available yet via gRPC for Core Lightning (v0.11.2 and master). For now, we can just return a custom Unimplemented or equivalent error.

[Dolu89]

We should change "get" to "decode" as "get" might mean we are querying an existing invoice in the node database.

Also, FYI the decodepay method isn't available yet via gRPC for Core Lightning (v0.11.2 and master). For now, we can just return a custom Unimplemented or equivalent error.

I think we need both get and decode.

• get for querying an existing invoice from the node => can get settled information
• decode for decoding any invoice => can't get settled information

[louneskmt]

Gotcha, opened #22 to track the decode feature.