Process a mid-term policy endorsement through Socotra's Endorsements API

Steps

1. Define the allowed endorsement names/types for the product in its policy/endorsements.json configuration before any endorsement can be created.
2. Create an endorsement transaction against the active policy and modify the fields being changed (coverage, limits, insured details, etc.).
3. Quote the endorsement to calculate the premium delta from the change.
4. Accept the endorsement to bind it; an invoice is issued automatically once the transaction reaches accepted state.
5. If the endorsement needs to be undone after acceptance and its invoice is later invalidated, confirm the associated payment is auto-reversed rather than manually adjusting billing.