Add COH to /candidates/totals/by_office endpoint

[JonellaCulmer]

What we're after:
We need to add cash on hand to /candidates/totals/by_office endpoint so that we may be able to display cash on hand on the House and Senate summary tables on the overview pages.

Endpoint:
https://api.open.fec.gov/v1/candidates/totals/by_office/?api_key=DEMO_KEY&office=S&election_year=2022&is_active_candidate=true&per_page=20&sort_null_only=false&sort_hide_null=false&sort_nulls_last=false&page=1

Related issue:
#5026

Completion criteria:

• COH now available on /candidates/totals/by_office endpoint
• Followup ticket for front-end implementation is created

Designs:

[patphongs]

This endpoint is what will be used for the COH: https://api.open.fec.gov/v1/candidates/totals/aggregates/?aggregate_by=office&election_year=2022&election_full=true&is_active_candidate=true&per_page=100&office=H&api_key=DEMO_KEY

[JonellaCulmer]

Followup implementation ticket here: fecgov/fec-cms#5215