Move the Repository module of the mediator-coordination crate to a separate crate

[Hermann-Core]

• Since some dependencies will use the database for persisting data, it might be worth moving the Repository module in the mediator-coordination to a separate crate for flexibility and scalability.

• I also noticed some unnecessary code duplication within the repository implementation. We could provide default implementations for the methods of the Repository trait. Since many implementations will likely use these defaults, this would reduce the need for re-implementations.

@IngridPuppet could you clarify where the forward messages are persisted in the mediator? I couldn’t find this part while reviewing the mediator-coordination code.

[IngridPuppet]

@IngridPuppet could you clarify where the forward messages are persisted in the mediator? I couldn’t find this part while reviewing the mediator-coordination code.

This depends on:

• Implement the forward protocol for the pop-server #41