Introduce interface for CC service cut off dates

What does this MR do and why?

Context

With the ability to receive and store the information about Cloud Connector services (for now: name and the service start date) from CDot, we need to provide a simple API to read into that data.

To unblock groupai framework work on Duo Chat, we explained to them how to access the "raw" (JSON) data here (internal).

As a temporary solution, the team introduced the wrapper around this data in model.

Intent

We need a single entry/access point for Cloud Connector data and interactions.
This should not be a Rails model because CC features span over multiple models.

A great candidate can be CloudConnector::AccessService (code)

Implementation

We waited until !142800 (merged) and !143037 (merged) are merged to avoid conflicts and interruptions for groupai framework.

Now that it is done, we extract the interface they introduced in a model into the Cloud Connector Access Service.

MR acceptance checklist

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How to set up and validate locally

This is a refactoring, so we keep the existing logic unchanged.
For the manual testing, we could test the Duo Chat locally.

Related to #438276 (closed)