docs: update api urls (#2074)

* Update homepage.md

* Update add-fulfillment-provider.md

* Update gatsby-medusa-starter.md

* Update how-to-create-notification-provider.md

* Update how-to-create-payment-provider.md

* Update how-to-implement-checkout-flow.mdx

* Update nextjs-medusa-starter.md

* Update paypal.md

* Update quick-start.md

* Update stripe.md

* Update docs/content/advanced/backend/shipping/add-fulfillment-provider.md

Co-authored-by: Shahed Nasser <shahednasser@gmail.com>

* Update docs/content/quickstart/quick-start.md

Co-authored-by: Shahed Nasser <shahednasser@gmail.com>

* Update docs/content/advanced/backend/shipping/add-fulfillment-provider.md

Co-authored-by: Shahed Nasser <shahednasser@gmail.com>

Co-authored-by: Danijel Predojevic <danijel@vivant.eco>
Co-authored-by: Shahed Nasser <shahednasser@gmail.com>

docs/content/starters/gatsby-medusa-starter.md

@@ -108,6 +108,6 @@ The Gatsby storefront comes with a lot of features out of the box including:
 
 ## What’s Next 🚀
 
-- Check the [Storefront API reference](https://docs.medusajs.com/api/store/auth) for a full list of REST APIs to use on your storefront.
+- Check the [Storefront API reference](https://docs.medusajs.com/api/store) for a full list of REST APIs to use on your storefront.
 - Learn how to [deploy the Gatsby storefront on Netlify](../deployments/storefront/deploying-gatsby-on-netlify.md).
 - Learn how to add [Stripe as a payment provider](../add-plugins/stripe.md#gatsby-storefront).

docs/content/starters/nextjs-medusa-starter.md

@@ -213,5 +213,5 @@ You can learn more about development with Next.js through [their documentation](
 
 ## What’s Next 🚀
 
-- Check the [Storefront API reference](https://docs.medusajs.com/api/store/auth) for a full list of REST APIs to use on your storefront.
+- Check the [Storefront API reference](https://docs.medusajs.com/api/store) for a full list of REST APIs to use on your storefront.
 - Learn [how to install Medusa Admin](../admin/quickstart.md).