Add an endpoint returning a list of all workers

Description

Introduces an endpoint where an administrator can request a list of connected workers.

Changes

None.

Additions

The endpoint and its test.

Test and Review

To be filled in by the reviewers

• All of the methods are commented to expectation

• The methods are tested to satisfaction

• There are no unnecessary files added to the PR

• The continuous integration has no problems with the PR

• The PR is filled in as requested e.g. labels added reviews requested

• The documentation is up-to-date

• All nullable parameters are marked as such