Add option to specify label/description when sending a payment to a keysend address

[cat-bytes]

Describe the bug
Add option to specify label/description when sending a payment to a keysend address.

c-lightning REST api "/pay/keysend" has a "label" parameter for specifying label/description.

Be nice to scroll through payment history and have descriptions for what I paid for!

To Reproduce
Steps to reproduce the behavior:
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Expected behavior
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Screenshots
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Desktop (please complete the following information):
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Smartphone (please complete the following information):

• Device: iPhone 8
• OS: [e.g. iOS14.4]
• Zeus Version v0.5.0-beta3

Additional context
Using c-lightning REST interface

[kaloudis]

We now have an internal notes feature you can use for this

[myxmaster]

After #2723 is merged, it is all done for LND.

CLN is todo though (I didn't look into CLNs capabilities of keysend and keysend message).

[kaloudis]

OP is talking internal memos. This is already supported. Closing.

Feel free to reopen if you don't think the current functionality addresses your use case.