fix(data-connect): include debugDetails in GraphQL error messages

[mtr002]

Description

When a Data Connect operation fails server-side (e.g., SQL runtime error or connection quota issues), the backend returns a generic message: "SQL execution failed" alongside detailed diagnostics in extensions.debugDetails.

Currently, DataConnectApiClient.makeGqlRequest extracts only error.message, completely discarding extensions.debugDetails. As a result, standard Node.js logging only surfaces "SQL execution failed" with no actionable cause.

Issue: firebase/firebase-tools#11068

Changes

• In DataConnectApiClient.makeGqlRequest, format GraphQL errors to append error.extensions.debugDetails to error.message when present.
• In DataConnectApiClient.toFirebaseError, format data.errors when present on non-200 HTTP responses rather than falling back to "Unknown server error".
• Zero public API or type changes; FirebaseDataConnectError remains unchanged.

Testing

• Added unit tests in data-connect-api-client-internal.spec.ts for:
  • GraphQL errors with extensions.debugDetails.
  • Multiple GraphQL errors joined with ; .
  • Non-200 HTTP responses containing GraphQL error arrays.
• Verified with npm run lint and npm test.

[gemini-code-assist]

Code Review

This pull request refactors GraphQL error handling in the Data Connect API client by introducing a new helper function, formatGraphqlErrors, which formats errors and appends debugDetails when available. It also adds support for parsing and formatting GraphQL errors from non-200 HTTP responses, backed by comprehensive unit tests. The reviewer suggested using optional chaining within the formatting helper to prevent potential runtime crashes if malformed error objects are received.

[stephenarosaj]

LGTM