Fix/1476 create parent approvals for old parent accounts

[duncanc19]

Issue

CQC providers with missing child workplaces should see the 'Have you added all your workplaces?' message after they have been a parent for more than eight weeks. Investigation found that some old accounts did not have a record for when they became a parent, so this PR adds records for parent approval to these accounts so that they can see these messages.

Work done

• Created database migration to add become a parent records to parent workplaces with no approval record

Tests

Does this PR include tests for the changes introduced?

• Yes
• No, I found it difficult to test
• No, they are not required for this change