feat(graphql): extract operationType from the req. body

[mortargrind]

Resolves: #4563

Motivation

Persisted GraphQL operations do not have a query property that contains the full operation string. As a result operationType cannot be extracted for them.

Changes

An alternative way of extracting operationType from a dedicated operationType param is added. The current way of extracting the value has higher precedence over this new alternative.

Test instructions

Manual testing: If a GraphQL request has operationType in its body or in query params as 'query'|'mutation'|'subscription' and operationType cannot be extracted from the query property.

Checklist

• Tested locally
• Tested on staging
• Added unit tests for this change.
• Added e2e/integration tests for this change.
• Updated documentation and/or relevant AGENTS.md file

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[mortargrind]

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