NPA-5116 Add API Authentication Documentation

[JackPlowman]

Pull Request

Ticket Link

https://nhsd-jira.digital.nhs.uk/browse/NPA-5116

Description/Change Summary

Updated specification

• Add generic API authentication documentation
• Add per endpoint authentication documentation
• Docs should align with this table - https://nhsd-confluence.digital.nhs.uk/spaces/NPA/pages/1018846943/API+endpoints+overview

e.g.

How to test?

Review Checklist

ℹ️ This section is to be filled in by the reviewer.

• I have reviewed the changes in this PR and they fill all or part of the acceptance criteria of the ticket, and the code is in a mergeable state.
• If there were infrastructure, operational, or build changes, I have made sure there is sufficient evidence that the changes will work.
• I have ensured the changelog has been updated by the submitter, if necessary.

Post-merge

After merging and deploying changes to the sandbox, Postman collection or spec examples please run the Run Postman collection workflow.

This will run the tests within the collection to check that the sandbox is working as expected once deployed.

[github-actions]

This branch is work on a ticket in the NHS Digital NPA JIRA Project. Here's a handy link to the ticket:

NPA-5116

[github-actions]

This branch is work on a ticket in the NHS Digital NPA JIRA Project. Here's a handy link to the ticket:

NPA-5116

[github-actions]

This branch is work on a ticket in the NHS Digital NPA JIRA Project. Here's a handy link to the ticket:

NPA-5116

[github-actions]

This branch is work on a ticket in the NHS Digital NPA JIRA Project. Here's a handy link to the ticket:

NPA-5116

[ClarksonAdam]

Given that the links to the types are already in the sentence above, I think it would be better here to list the access modes against each of the types.

That way when they're listed against each endpoint, it makes a little more sense what they relate to without having to read this whole section:

For example:

## Security and authorisation

This API supports both [user-restricted](https://digital.nhs.uk/developer/guides-and-documentation/security-and-authorisation#user-restricted-apis) and [application-restricted](https://digital.nhs.uk/developer/guides-and-documentation/security-and-authorisation#application-restricted-apis) access types with the following access modes:

| Access mode                   | Access type            |
|-------------------------------|------------------------|
| Patient access                | User-restricted        |
| Healthcare worker access      | User-restricted        |
| Application-restricted access | Application-restricted |

...

[github-actions]

This branch is work on a ticket in the NHS Digital NPA JIRA Project. Here's a handy link to the ticket:

NPA-5116

[ClarksonAdam]

LGTM 👍