add failed payment email notifications #120

Job	Run time
compile-cln (v24.11, stable, ElementsProject, lightning)	20s
compile-cln (v24.08, stable, ElementsProject, lightning)	19s
Format Check	16s
Unit tests	25s
Clippy	13s
compile-cln (v24.05, 1.79.0, ElementsProject, lightning)	19s
compile-cln (v24.02.2, 1.79.0, ElementsProject, lightning)	17s
compile-cln (v23.11.2, 1.79.0, ElementsProject, lightning)	12s
Integration tests (v24.11)	1m 55s
Integration tests (v24.08)	1m 21s
Integration tests (v24.05)	1m 31s
Integration tests (v24.02.2)	1m 52s
Integration tests (v23.11.2)	1m 45s
	10m 45s

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