Splits a header value by commas if the header is defined as comma-separated.
Headers like Date, Last-Modified, Expires contain commas in RFC 7231 date
format (e.g., "Mon, 01 Jan 2024 12:00:00 GMT") and should NOT be split.
Parameters
headerName: string
The lowercase header name
value: string
The header value string
Returns string[]
Array of values (single element for non-comma-separated headers)
Splits a header value by commas if the header is defined as comma-separated. Headers like Date, Last-Modified, Expires contain commas in RFC 7231 date format (e.g., "Mon, 01 Jan 2024 12:00:00 GMT") and should NOT be split.