Add repository service to supervisor

[GMKrieger]

📚 Context

The repository is the central component of the Node, which every other service communicates with. It needs to be maintained by the supervisor, as an error with it needs to addressed and corrected ASAP for the Node to function properly.

✔️ Solution

The repository needs a service interface as defined in the services.go method start, that starts the repo and sends back the connection pool that's going to be used by the other services.

It needs to have a validation channel that triggers an error in case the service ever stops, for any reason, as without the repository, the Node cannot function and may arrive in an improper state. From this, it needs to be restart or the whole node shut down.

📈 Subtasks

• Create repository service
• Add it to the supervisor