Return GraphQL-formatted errors for upstream proxy failures

[coderabbitai]

Summary

Handle upstream fetch failures in the GraphQL proxy and return the existing client-readable GraphQL error shape.

Required changes

• Wrap the upstream fetch(apiUrl, ...) call in error handling.
• Return { errors: [...] } JSON with HTTP status 502 when the upstream request throws.

Affected areas

• api/graphql.ts

Acceptance criteria

• Network, DNS, and timeout failures do not produce an opaque platform 500 response.
• The response has HTTP status 502 and the expected JSON errors shape.
• The client error path can render the failure.

Source

• Review comment: Fix 404 error #34 (comment)
• Pull request: Fix 404 error #34
• Requested by: @Alejandroq12

[coderabbitai]

Technical note

Distinguish an upstream transport failure from an upstream GraphQL error response. Catch only a rejected fetch or timeout and map it to the documented 502 GraphQL-shaped response. If upstream returns a valid GraphQL errors payload, pass it through. Do not expose tokens, URLs, or raw internal error details.

Reference: MDN: fetch() exceptions

[coderabbitai]

Engineering note

Separate transport failure from an upstream GraphQL error response. fetch() rejects for network failures, but an HTTP error response still resolves. Convert only thrown transport failures to the documented 502 GraphQL error shape, and preserve valid upstream error payloads.

Read: MDN: Using the Fetch API