fix: return same tokens if not expired

[sabhas]

Issue

closes #279

Intent

• if valid tokens exist for a specific clientId and UserId, return those tokens instead of generating new tokens

Implementation

• before generating new tokens check if valid tokens exist in DB then return existing tokens.

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.

[sasjsbot]

:tada: This PR is included in version 0.21.3 :tada:

The release is available on:

• GitHub release
• v0.21.3

Your semantic-release bot :package::rocket: