Update Postman Collection

[MRichards99]

Description:
The Postman collection needs updating to reflect changes across this repo.

The search API endpoints need to be added (or put into their own collection?), remembering that the endpoints have capitalised first letters (e.g. /Documents/count).

We should also add the concept of prefixes into the collection to be able to differentiate between the search API and DG API prefixes - otherwise you have to change the variable every time you want to switch between the two. You could call the variables search_api_prefix and datagateway_api_prefix. This would be the time to look into whether Postman environments would be better to control this stuff, instead of using variables.

In the 'Frequently Used Requests' folder, the 'Users By Filter' request has some example responses. As they are unused and the examples are from the DB backend, these should be removed and check across the entire collection to see if there are other example responses - remove these also. It looks like there's a lot of them across the 'Other Entity Requests' folder, probably where bulk duplication happened. A new version of Postman is good at picking this up (e.g. v10.12.10), whereas an older version (e.g. v7.36.6) doesn't show this in the sidebar.

When querying the ISIS DG API, you have to add s to http for it to work. This should be resolved - I think taking the http into the datagateway-api variable would be the best way to do that and removing the http:// from each of the requests.

It would be nice to add URLs to the production/dev instances to make it easier to access those straight away.

I believe Postman has some kind of Git support these days, which might make it easier to keep changes synced in the future. Explore this and maybe even look to see what Insomnia does.

Acceptance criteria:

• Add search API endpoints
• Add variables for search API prefix and DataGateway API prefix
• Remove example responses
• Extract http:// into datagateway-api variable
• Add prod/dev URLs for DG API
• Explore possible Git support