Cannot sum payment amount as plugin is serialized

Problem/Motivation

If someone wants to sum the total amounts of payments in an aggregated view, there is no way to do this as the payment amount is stored on a line item plugin which gets serialized in the database.

Proposed resolution

Add a total_amount field to the payment entity which is updated on entity save.

Remaining tasks

• Add new field in update hook
• Add post update to save existing payments
• Add views data

User interface changes

None

API changes

New field on payment entity

Data model changes

New field on payment entity