fix: Correct GraphQL mutation format for Transactions.Delete()

[eshaffer321]

Summary

Fixes the Transactions.Delete() method which was returning BAD_REQUEST errors due to incorrect GraphQL mutation format. The mutation now matches the Python client and Monarch API expectations.

Root Cause

The Go client was using:

mutation DeleteTransaction($id: UUID!) {
  deleteTransaction(id: $id) { ... }
}

With variables: {"id": "txn-123"}

But the Monarch API expects (matching Python client):

mutation Common_DeleteTransactionMutation($input: DeleteTransactionMutationInput!) {
  deleteTransaction(input: $input) { ... }
}

With variables: {"input": {"transactionId": "txn-123"}}

Changes

• ✅ Fixed GraphQL mutation in internal/graphql/queries/transactions/delete.graphql
• ✅ Updated pkg/monarch/transactions.go to use input wrapper format
• ✅ Added comprehensive test coverage (TestTransactionService_Delete, TestTransactionService_Delete_Error)
• ✅ Created examples/transaction_deletion.go with:
  • Delete method usage and error handling
  • hideFromReports workaround for bank-imported transactions
  • Real-world example: Walmart multi-delivery consolidation
• ✅ Updated CHANGELOG.md with fix details
• ✅ Updated go.mod/go.sum dependencies

Test Results

All tests pass ✅ (54 tests, 1 skipped):

PASS
ok      github.com/eshaffer321/monarchmoney-go/pkg/monarch    0.207s

Breaking Changes

None - this is a bug fix that makes the existing API work as intended.

Additional Notes

The error handling already captures both Code and Message from the API response, so detailed error messages will now be visible when deletion fails (e.g., for bank-imported transactions that cannot be deleted).

For transactions that cannot be deleted, users can use the HideFromReports field as an alternative (documented in the new example file).

Related Issues

Resolves issue where bank-imported transactions couldn't be deleted in Walmart multi-delivery consolidation tool.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 44.55%. Comparing base (2e51ad7) to head (6bec196).
⚠️ Report is 1 commits behind head on main.

❌ Your project status has failed because the head coverage (44.55%) is below the target coverage (70.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #17      +/-   ##
==========================================
+ Coverage   43.18%   44.55%   +1.36%     
==========================================
  Files          15       15              
  Lines        2239     1663     -576     
==========================================
- Hits          967      741     -226     
+ Misses       1198      846     -352     
- Partials       74       76       +2     

Flag	Coverage Δ
unittests	44.55% <100.00%> (+1.36%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
pkg/monarch/transactions.go	72.31% <100.00%> (+4.23%)	⬆️

... and 14 files with indirect coverage changes

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