Make a go module for the client

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Preflight Checklist

• I have searched the issue tracker for an issue that matches the one I want to file, without success.

Problem Description

The Go client for openmeter pulls in the entire openmeter project with all dependencies, which can generate a lot of conflicts and forced upgrades.

Proposed Solution

Create a new go module for the client with a more limited set of dependencies.

Alternatives Considered

Don't use the Go client, just do http calls directly

Additional Information

No response