Add functionality to negotiate contracts and receive files from other connectors

As a user, I would like to be able to negotiate contract with other user (connector) so that I can receive files from that user.

There should be a button or an option to be able to negotiate contract in the frontend.
In the Download section, user should be able to download the received files from the other connectors.
DoD General Criteria
Feature has been merged into the main branch
Feature has been added to the documentation
Product owner approved features
Developers agreed to release

amosproj / amos2024ss02-international-dataspace-station