Dividends show N/A for "Investment amount"

[nyomanjyotisa]

ref: https://chat.google.com/room/AAQAWojMDVI/N3ohaxAUcoM/N3ohaxAUcoM?cls=10

Problem

Dividend records show "N/A" for "Investment amount" columns on /equity/dividends page. Historical dividends are missing investment_amount_cents data.

Solution

Create a one time script to backfill investment_amount_cents fields on dividends table. And update the field to not nullable after backfilled

Related PR #796

Comment from the PR author #796 (comment)