Reduce payload size for cart methods

[filipsobol]

Short Description of the PR

When cart methods are called, we include the whole cart object in the payload sent to the api-client (Server Middleware). This becomes an issue when the cart contains multiple items and uses custom queries to add more properties to it, resulting in an HTTP 413 Payload Too Large error.
This PR fixes it by only sending data that is needed - cart id and version.

Pull Request Checklist

• I have updated the Changelog (V1) v2 and mentioned all breaking changes in the public API.
• I have documented all new public APIs and made changes to existing docs mentioning the parts I've changed so they're up to date.
• I have tested my Pull Request on production build and (to my knowledge) it works without any issues
• I have followed naming conventions