OC-997: Bring pubrouter lambda into serverless deployment

[finlay-jisc]

The purpose of this PR was to make the pubrouter function easier to develop with by moving it in with the rest of the API code, while it had previously lived with the terraform code.

This also allowed us to have a local "version" of the function, triggered by hitting the API instead of by an S3 create event.

For the most part the function code hasn't changed, except:

• it now lives in the api/components/pubRouter directory
• it has had some typing added to it
• there is some conditional logic for dealing with incoming params from a local API invocation
• the more "controllery" logic has been put in the controller file whereas previously it was all one function

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Acceptance Criteria:

• The pubrouter function is part of the API codebase
• It still works as it did previously on deployed environments

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Checklist:

• Local manual testing conducted
• Automated tests added
• Documentation updated

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Tests:

API

E2E

[adwearing-jisc]

Lovely stuff