Add CSV download for Saved Accessions

[helrond]

Is your feature request related to a problem? Please describe.

The Collections Management team uses a secondary system to track accessions so they can easily report data about size over a particular time period. Although this data is currently available in the "Saved Accessions" tab in Aurora, it is not easily exportable. Additionally, the lack of a uniform unit for size requires additional interpretation.

Describe the solution you'd like

Add the ability to download a CSV of saved accessions (like there is for transfers). This spreadsheet should include all the fields that are in the Saved Accessions table:

• Title
• Date created
• Extent (in GB)
• Status
  As well as (potentially) some additional fields
• The four-part AS accession identifier
• The AS resource the accession is associated with