BUG/MINOR: spec: use string type for storage GET file responses #1259

Job	Run time
generate-models	1m 28s
HAProxy check commit message	5s
generate-specification	1m 4s
license-check	0s
lint-spec	0s
go mod tidy	0s
Test equal	0s
golangci-lint	0s
Build	0s
Tests	0s
e2e on HAProxy	0s
	2m 37s

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