REORG/MINOR: uniforming cluster-configuration header to string #509

Job	Run time
generate-models	1m 2s
generate-specification	43s
HAProxy check commit message	0s
Build	22s
license-check	21s
golangci-lint	59s
lint-spec	6s
go mod tidy	8s
Tests	2m 25s
e2e on HAProxy (2.1)	44s
e2e on HAProxy (2.2)	42s
e2e on HAProxy (2.3)	43s
e2e on HAProxy (2.4)	42s
e2e on HAProxy (2.5)	48s
e2e on HAProxy (2.6)	41s
e2e on HAProxy (2.7)	42s
e2e on HAProxy (2.8)	41s
	11m 49s

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