Update RCPCH public Postman Collection for the dGC API

[pacharanero]

Postman are improving the Git integration of their API definitions:

Dear Postman User,

We noticed that you and your team have been using an older version of schema sync integration to sync your API specification between Postman and your repository. We wanted to inform you that we have recently launched a new and improved method of syncing your APIs to your repository.

Effective April 15th 2023, the old schema sync integrations will stop working. We suggest you to move to the native git integration that has enhanced capabilities of syncing collections along with schema and also provides you more control over when the syncing happens.

We highly recommend that you switch to the new schema sync integration as soon as possible. Our team is available to assist you with any questions or concerns you may have during this transition.

ACTION: We need to check through the public Postman collection for dGC API and ensure it is correctly configured for the new system.

[pacharanero]

As part of this review, we should also make sure that the Postman collection can be used as a simple test runner.
There is a command line client (newman) which can be used to run Postman collections in the terminal.