feat: replace ID with UID

[sabhas]

BREAKING CHANGE: remove auto incremental ids from user, group and permissions and add a virtual uid property that returns string value of documents object id

Issue

closes #361

Intent

replace ID with UID

Implementation

add a virtual property to models that returns string value of _id

Checks

• [ ] Code is formatted correctly (npm run lint:fix).
• [ ] Any new functionality has been unit tested.
• [ ] All unit tests are passing (npm test).
• [ ] All CI checks are green.
• [ ] Reviewer is assigned.