RESTful-style API handler should support filtering with "null" for nullable fields

[ymc9]

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[hasan-aa]

I think not equal operator is not supported as well which I think is needed. As a workaround I did this for now:

const NotPending = [
  TransactionStatus.APPROVED,
  TransactionStatus.REJECTED,
  TransactionStatus.CANCELLED,
  TransactionStatus.POOL,
].join(",");

Please let me know if I need to open a new issue record for this.