Adding claimDate to cmp metadata on backup submission

[kylesoskin]

Summary

• Adding a claimDate to backup paper 526 submissions at request of CMP and MAS team
• This allows them to properly set the DOR

Related issue(s)

department-of-veterans-affairs/va.gov-team#50111

Testing done

local/rspec

What areas of the site does it impact?

backend

Acceptance criteria

• I fixed|updated|added unit tests and integration tests for each feature (if applicable).
• No error nor warning in the console.
• Events are being sent to the appropriate logging solution
• Documentation has been updated (link to documentation)
• No sensitive information (i.e. PII/credentials/internal URLs/etc.) is captured in logging, hardcoded, or specs
• Feature/bug has a monitor built into Datadog or Grafana (if applicable)
• If app impacted requires authentication, did you login to a local build and verify all authenticated routes work as expected
• I added a screenshot of the developed feature

[rbeckwith-oddball]

Ruby syntax-wise, it looks good.