Fix Manually Created Scanner Data

Why are we doing this work

This is a follow-on from Find or initialize Scanners using project_id (!82923 - merged):

Fixing this 100% will require a data migration which will be performed later on.

The original bug was that vulnerabilities created using the GraphQL API linked to whatever manual scanner was created in the database first. We need to do a data migration to create new scanners for projects that have manually created vulnerabilities.

Relevant links

• Issue with initial bug discovery: Vulnerabilities created via GraphQL mutation ar... (#353176 - closed)
• Bug fix issue: Manually created vulnerabilities link to wrong ... (#355802 - closed)

Non-functional requirements

• Testing: Tests needed for migration

Implementation plan

• database Create post-migration that will find manually created vulnerabilities from projects that don't have the manual creation scanner, then create a scanner for each project