USF-1323: Added new checkout API functions

src/content/docs/dropins/checkout/checkout-functions.mdx

@@ -11,9 +11,38 @@ import OptionsTable from '@components/OptionsTable.astro';
 
 This topic provides the details and instructions you need to use the functions provided by the Checkout dropin.
 
+## authenticateCustomer
+
+The `authenticateCustomer` function manages the authentication state of a customer, either by fetching customer data using the [`getCustomer`](#getcustomer) function when authenticated or resetting the customer data when not authenticated.
+
+```ts
+export const authenticateCustomer: () => Promise<void>
+```
+
+### Returns
+
+The function does not return any value explicitly; it performs side effects by fetching data and logging errors.
+
+### Usage
+
+See the following example for usage details:
+
+```ts
+import { authenticateCustomer } from '@/checkout/api/authenticateCustomer';
+
+async function authenticate() {
+  try {
+    await authenticateCustomer();
+    console.log('Customer authenticated successfully.');
+  } catch (error) {
+    console.error('Error authenticating customer:', error);
+  }
+}
+```
+
 ## estimateShippingMethods
 
-This function fetches and displays available shipping methods based on a customer's address information. It can take a combination of fields as `criteria`: country, region, region identifier, and postal code.
+The `estimateShippingMethods` function fetches and displays available shipping methods based on a customer's address information. It can take a combination of fields as `criteria`: country, region, region identifier, and postal code.
 
 It uses a utility function to call an [`estimateShippingMethods`](https://developer.adobe.com/commerce/webapi/graphql/schema/cart/mutations/estimate-shipping-methods/) mutation.
 
@@ -660,4 +689,26 @@ setShippingMethodsOnCart([
     method_code: 'flatrate',
   },
 ]);
+```
+
+## synchronizeCheckout
+
+The `synchronizeCheckout` function synchronizes the checkout state with the current cart information. It ensures that the checkout process is properly initialized, reset, or updated based on the cart data. It uses the [`getCart`](#getcart) function to fetch the necessary cart details.
+
+```ts
+export const synchronizeCheckout: () => void
+```
+
+### Returns
+
+The function does not return any value explicitly; it performs side effects by fetching data and logging errors.
+
+### Usage
+
+See the following example for usage details:
+
+```ts
+import { synchronizeCheckout } from '@/checkout/api/synchronizeCheckout';
+
+synchronizeCheckout('IeTUiU0oCXjm0uRqGCOuhQ2AuQatogjG');
 ```