-c
is what you likely need
Using the output you posted above, you can process it further:
jq -c . input
To Give;
{"key":"SEA-739","status":"Open","assignee":null}
{"key":"SEA-738","status":"Resolved","assignee":"[email protected]"}
Or you can just change your original command
FROM
jq -r '(.issues[] | {key, status: .fields.status.name, assignee: .fields.assignee.emailAddress})'
TO
jq -c '(.issues[] | {key, status: .fields.status.name, assignee: .fields.assignee.emailAddress})'