Use graphql.HasOperationContext in arangodb assembler

[ridhoq]

Description of the PR

It seems we're not entering the logic to determine what graphql fields are present in some of the arangodb methods. This is because we are checking ctx.Value("graphql").(graphql.OperationContext) which isn't actually present. This is because the operation context is stored using the value operation_context as seen here. Instead of doing this logic here, we can just call the HasOperationContext function provided by the gqlgen library.

PR Checklist

• All commits have a Developer Certificate of Origin (DCO) -- they are generated using -s flag to git commit.
• All new changes are covered by tests
• If GraphQL schema is changed, make generate has been run
• If collectsub protobuf has been changed, make proto has been run
• All CI checks are passing (tests and formatting)
• All dependent PRs have already been merged

[mihaimaruseac]

Nice catch!

[pxp928]

LGTM. Good catch on that