MINOR: add support for acme keyword reuse-key #1002

Job	Run time
generate-models	1m 44s
generate-specification	1m 9s
HAProxy check commit message	0s
golangci-lint	1m 18s
lint-spec	13s
Build	36s
go mod tidy	16s
license-check	41s
Tests	52s
Test equal	1m 15s
e2e on HAProxy (2.3)	52s
e2e on HAProxy (2.2)	52s
e2e on HAProxy (2.4)	59s
e2e on HAProxy (2.8)	49s
e2e on HAProxy (2.1)	50s
e2e on HAProxy (2.6)	52s
e2e on HAProxy (2.7)	57s
e2e on HAProxy (2.5)	55s
	15m 10s

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