Cloud Hub - Category refactor

Cloud Hub is looking to refactor an endpoint for our category reporting. This endpoint returns all of the apps a company has spent money on and groups them by category. We want to expand this endpoint to also group apps by subcategory. An example data structure is below, but the numbers are not accurate and are just placeholders.

Current structure:

{
    "category": "Marketing",
    "spend": 775982.01,
    "apps": [{
        "company_app_id": "48a393cf-d4cf-4c33-8621-a7eb370972ca",
        "app_id": "2e043679-f764-47e0-afc3-ee39c51a2033",
        "app_label": "Adobe Campaign",
        "app_domain": "adobe.com",
        "spend": 176987
    }]
}

New structure:
{
    "category": "Marketing",
    "spend": 775982.01,
    "subcategory": [{
        "subcategory": "Email Marketing",
        "spend": 123456789,
        "apps": [{
            "company_app_id": "48a393cf-d4cf-4c33-8621-a7eb370972ca",
            "app_id": "2e043679-f764-47e0-afc3-ee39c51a2033",
            "app_label": "Adobe Campaign",
            "app_domain": "adobe.com",
            "spend": 176987
        }]
    }]
}

Requirements
1. Update companyAppService.getTopSpendCategories to group by companyapps.subcategory too.
2. subcategory.spend should be the total spend for any apps with that same subcategory, this is the same as category spend.
3. Update tests to reflect new structure and validate summary is working correctly.
 

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2. Please include a git patch for easier integration of changes.
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