GraphQL subscriptions `mutation_type` is always UPDATE

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Description

When subscribing to an entity, the mutation_type seems to always be UPDATE, at least for newly created entity

Details

These details can help to reproduce the environment the issue is occurring

Local Environment: node v20.15.1 Query Version: @subql/query@^2.15.2 Indexer Version: @subql/node-ethereum@^5.1.7 Network Details:

• anvil local test chain

Steps to Reproduce

1. subscribe to any model
2. create an entity
3. the subscription message payload contains a mutation_type set to UPDATE

Expected behavior: mutation_type should be INSERT Actual behavior: mutation_type is UPDATE