* Support JIT invoicing on donations to rewards pool
Now you can just-in-time fund your account to donate to SN's reward pool.
You can also donate without an account via the @anon account, also using
JIT invoices.
* Ensure donate amount is numeric
* Explicit error checking for hash being required for invoice validation
* let donation exceptions bubble for jit funding
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Co-authored-by: keyan <keyan.kousha+huumn@gmail.com>
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