Put vulnerability finding link ingestion behind feature flag

What does this MR do and why?

This MR puts vulnerability finding link creation in the new ingestion service behind a feature flag until we can enable the unique index constraint. I ran a BG migration last week to clear out the table completely, and I didn't realize we were still writing to the table. I’ll be repopulating it with another BG migration after I put in the unique constraint. By having it completely empty, it greatly simplifies the migration so I don’t have to do any checks for duplicates or existing data.

Screenshots or screen recordings

N/A

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #330882 (closed)