Refactored functionality of handle_paid_invoice into mint. #1038

Job	Run time
Build WASM (stable, -p cdk)	1m 23s
Build (stable, -p cdk)	1m 36s
Format	3s
Build WASM (stable, -p cdk --no-default-features)	1m 12s
Build (stable, -p cdk --no-default-features)	1m 1s
Build WASM (stable, -p cdk --no-default-features --features wallet)	1m 17s
Build (stable, -p cdk --no-default-features --features wallet)	1m 22s
Build WASM (stable, -p cdk-js)	1m 38s
Build (stable, -p cdk --no-default-features --features mint)	1m 7s
Build (stable, -p cdk-redb)	1m 32s
Build (stable, -p cdk-sqlite)	2m 0s
Build (stable, -p cdk-axum)	1m 13s
Build (stable, -p cdk-cln)	1m 21s
Build (stable, -p cdk-fake-wallet)	1m 7s
Build (stable, -p cdk-strike)	1m 20s
Build (stable, --bin cdk-cli)	2m 2s
Build (stable, --bin cdk-mintd)	1m 44s
Build (stable, --examples)	1m 48s
	24m 46s

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