Fix for usnat supported api lookup (#1804)

## Why?

Since 19/11/2034 ~ 18:00 UTC the consent state property `doNotSell` is
being set to true for all US users regardless of their consent choice.
This mean third party integrations that check for `doNotSell` before
loading are not running e.g. prebid, comscore and a9 (Amazon ads).

### gppData

We read the `gppData` object as provided by Sourcepoint:

<img
src="https://github.com/user-attachments/assets/fec25081-79dc-4e89-b19e-d7c032f91061"
width="300px" />

### supportedAPIs string

In order to lookup the usnat metadata we read the
`gppData.supportedAPIs` property and split the string to set the
`supportedAPIs` string (e.g. `usnat`)

### supportedAPIs lookup

We then use the `supportedAPIs` string to lookup the property on
`gppData.parsedSection[supportedAPIs]`

However currently the `supportedAPIs` string is resolving to `usnat` but
the property on `gppData.parsedSection` is `usnatv1`

This causes the lookup to fail and sets `doNotSell` to true.

## What are you changing?

This change updates the logic so rather than using the `supportedAPIs`
string it directly attempts to read the first object in
`gppData.parsedSection`.

.changeset/silver-taxis-learn.md

@@ -0,0 +1,5 @@
+---
+'@guardian/libs': patch
+---
+
+Fix cmp usnat supported api lookup

libs/@guardian/libs/src/consent-management-platform/usnat/getConsentState.test.js

@@ -7,6 +7,9 @@ import { getConsentState } from './getConsentState.ts';
 jest.mock('./api');
 
 describe('getConsentState', () => {
+	beforeEach(() => {
+		jest.clearAllMocks();
+	});
 	it('gets the gpp consent state correctly - doNotSell is false', async () => {
 		getGPPData.mockResolvedValue(gppDataCanSell);
 

libs/@guardian/libs/src/consent-management-platform/usnat/getConsentState.ts

@@ -4,15 +4,12 @@ import { getGPPData } from './api';
 export const getConsentState: () => Promise<USNATConsentState> = async () => {
 	let doNotSell = false; // Opt-Out
 	const gppData = await getGPPData();
+	const supportedAPI = Object.values(gppData.parsedSections)[0];
 
-	const supportedAPIs = gppData.supportedAPIs[0]?.split(':')[1]; // E.G: '7:usnatv1', '8:uscav1'
-
-	if (supportedAPIs) {
-		//0 Not Applicable. SharingOptOutNotice value was not applicable or no notice was provided, 1 Opted Out, 2 Did Not Opt Out
-		doNotSell =
-			gppData.parsedSections[supportedAPIs]?.SaleOptOut !== 2 ||
-			gppData.parsedSections[supportedAPIs].Gpc;
+	if (supportedAPI) {
 		// https://github.com/InteractiveAdvertisingBureau/Global-Privacy-Platform/blob/main/Sections/US-National/IAB%20Privacy%E2%80%99s%20National%20Privacy%20Technical%20Specification.md
+		// 0 Not Applicable. SharingOptOutNotice value was not applicable or no notice was provided, 1 Opted Out, 2 Did Not Opt Out
+		doNotSell = supportedAPI.SaleOptOut !== 2 || supportedAPI.Gpc;
 	}
 
 	return {