[ECR] [request]: Filtering for Image Scan Results

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**Tell us about your request**
Provide the customers with the ability to filter scan results by "Severity" and "Image Age".

**Which service(s) is this request for?**
ECR

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
"We have 100s of repos with 1000s of images. This means we’d have to return tens (or 100s?) of thousands of results and then parse through them to come up with anything actionable. Ideally there would be filters for the severity of the findings and/or the age of the image."

**Are you currently working around this issue?**

**Additional context**

**Attachments**
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The issue concerns AWS ECR image scan results but names no repository files, tests, or implementation entry points. Start by reviewing the ECR roadmap context and existing scan-result filtering capabilities. Done would require an agreed design and delivered filtering by Severity and Image Age.

Written by the indexing model from the issue text.