EAR-2112 - Looping grand calculated summary

[sudeepkunhis]

https://jira.ons.gov.uk/browse/EAR-2112

• For the Grand summary page, the runner schema must have the type as 'GrandCalculatedSummary' as given below.

{
"id": "grand-summary",
"type": "GrandCalculatedSummary",
"page_title": "Grand summary",
"title": "Grand summary",
"calculation": {
"operation": {
"+": [
{
"identifier": "summary1",
"source": "calculated_summary"
},
{
"identifier": "summary2",
"source": "calculated_summary"
}
]
},
"title": "Grand summary"
}
}