Volunteer API Hardening #20

Summary

The volunteer API could be made more robust by validating input earlier and handling failures explicitly.

Current behavior

• User input is interpolated directly into Airtable's filterByFormula.
• Request bodies are parsed without handling malformed JSON.
• The endpoint accepts any HTTP method.
• Email addresses are not validated before use.
• Airtable lookup/create failures are logged but do not affect the response, so the endpoint may still return success even when persistence fails.

Proposed improvements

• Restrict the endpoint to POST requests.
• Gracefully handle malformed request bodies.
• Validate email addresses before processing.
• Escape user input before constructing Airtable formulas.
• Return appropriate HTTP status codes when Airtable operations fail instead of silently continuing.

I'd be happy to work on this.