[Fix] Add draft payments count to disbursements stats in API response

ziyliu commented 3 months ago

~~Remove draft payments count in total_payments_remaining when calculating total successful payments % on the FE dashboard.~~
Introduce a field to response total_payments_draft separately.

[TODO: Why this change is being made. Include any context required to understand the why.]

[TODO or N/A]

[x] This PR has a reasonably narrow scope (if not, break it down into smaller PRs).
[x] This PR title and description are clear enough for anyone to review it.
[x] This PR does not mix refactoring changes with feature changes (split into two PRs otherwise).

[x] No new CONFIG variables are required -OR- the new required ones were added to the helmchart's values.yaml file.
[x] No new CONFIG variables are required -OR- the new required ones were added to the deployments (pr-preview, dev, demo, prd).
[x] No new SECRETS variables are required -OR- the new required ones were mentioned in the helmchart's values.yaml file.
[x] No new SECRETS variables are required -OR- the new required ones were added to the deployments (pr-preview secrets, dev secrets, demo secrets, prd secrets).

[x] This is not a breaking change.
[ ] This is ready for production.. If your PR is not ready for production, please consider opening additional complementary PRs using this one as the base. Only merge this into develop or main after it's ready for production!