fix(openreader): Use READ COMMITTED to allow the usage of PostgreSQL replicas

[HRGCompany]

SERIALIZABLE isolation is incompatible with PostgreSQL replicas, causing "cannot use serializable mode on a hot standby" errors when OpenReader is pointed at a read-only replica.

Since OpenReader only performs read queries, READ COMMITTED is sufficient and works correctly on both primary and replica servers.

This PR adds support for configuring transaction isolation levels in the OpenReader and GraphQL Server packages, giving users more control over their query transactions.

This allows distributing requests across replicas for read-only queries, while keeping indexers / processors pointing toward the primary server to avoid any overload.

Default value is set to SERIALIZABLE to ensure backward compatibility and avoid breaking changes.

[Copilot]

Pull request overview

Updates OpenReader’s transaction isolation level to be compatible with PostgreSQL read-only replicas (hot standby), avoiding cannot use serializable mode on a hot standby errors while keeping queries read-only.

Changes:

• Change OpenReader’s START TRANSACTION isolation level from SERIALIZABLE to READ COMMITTED for read-only transactions.

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[belopash]

Hey, sorry for the long time reply. Could you please implement it as a configurable option, so It coiuld be passed to the server via command options?

squid-sdk/graphql/graphql-server/src/main.ts

Line 17 in dd9d52b

program.description(`GraphQL server for squids`)

[HRGCompany]

Hey, sorry for the long time reply. Could you please implement it as a configurable option, so It coiuld be passed to the server via command options?

squid-sdk/graphql/graphql-server/src/main.ts

Line 17 in dd9d52b

program.description(`GraphQL server for squids`)

I’ve just pushed a new commit with the following changes. Would you mind reviewing it?

Key Updates:

• Made the setting configurable.
• Reset the default to SERIALIZABLE to ensure backward compatibility and avoid breaking changes.
• Fixed CockroachDB Docker Compose image version.

CockroachDB is updated from v21.2.9 → v23.2.2 (the old version was no longer available, which was blocking rush test).