[spydon]

Fixes #26

Problem

PostgrestQueryBuilder.upsert sends Prefer: resolution=ignore-duplicates when called with ignoreDuplicates: true, and resolution=merge-duplicates otherwise. The request dispatch only recognized merge-duplicates, so an upsert with ignoreDuplicates: true was classified as RequestType.insert and never reached _handleUpsert. The conflicting row was appended as a duplicate:

await mockSupabase.from('users').insert({'id': 1, 'name': 'John Doe'});
await mockSupabase.from('users').upsert(
      {'id': 1, 'name': 'James Bond'},
      ignoreDuplicates: true,
    );
await mockSupabase.from('users').select();
// before: [{id: 1, name: John Doe}, {id: 1, name: James Bond}]
// after:  [{id: 1, name: John Doe}]

Changes

• The POST dispatch now treats resolution=ignore-duplicates as an upsert alongside resolution=merge-duplicates. As a side effect, postgrestExceptionTrigger now receives RequestType.upsert rather than RequestType.insert for these requests, which is what it should have been.
• _handleUpsert reads the resolution from the Prefer header. When ignore-duplicates is requested, a row that matches the conflict target is left untouched and no new row is inserted. Rows that do not conflict are still inserted.
• Skipped rows are left out of the response body, matching what PostgREST returns for INSERT ... ON CONFLICT DO NOTHING RETURNING.

Tests

Three tests were added covering both reproductions from the issue (default id conflict target and an explicit onConflict column) plus a mixed batch where one row conflicts and one does not, asserting both the response body and the resulting table contents. The full suite passes, and dart format and dart analyze --fatal-warnings --fatal-infos are clean.