Implement public retrieval API with file format support

[mprpic]

A public API should be implemented that allows retrieval of archived records by CVE ID and archive interval, returning either of the supported formats (PNG, PDF, WARC).

Requirements:

• Create a way to retrieve archived content for a given CVE ID
• Support query parameters for interval selection (0, 3, 10, 30, 90 days), a specific reference, and specific format

Acceptance Criteria:

• Public can query archived content by CVE ID, interval, reference, format
• API files in specified formats
• Proper error handling for missing archives

[dwelch2344]

This will definitely be good to impl, though we've so far operated with no public access (given we don't have auth). We'd have to change that, which is fine by me but may require ops support. See #11's comments

[dwelch2344]

Today's AWG notes:

• Provide minimum:
  • Search (with filters)
  • 302 Redirect route (with support for choosing the interval)
• Archives are immutable*

[dwelch2344]

Point of consideration:

• Do we meter / put a grace period on "convenience redirect url"