[Backup-Service] Amend/Improve Swagger Documentation

We can use this MB to track the following improvements to the Backup Service swagger documentation:

1. Amend the names of a few endpoints. "/cluster/active/" should be changed to "/cluster/self/".
2. Amend the responses of repositories to be an array of Repositories and the response of taskHistory to be an array of TaskRun.
3. Add the Backup and Info data-structure and update the responses of repository info endpoint response from Error to Info.
4. Fix the indentation which was preventing the cloud credentials from being recognised as part of the requestBody in the active repository endpoint.