Retrieves the authenticated Customer (that matches the given email/password pair) if they are part of a specific Store.
If used with an optional [access token for an anonymous session](ctp:api:type:AnonymousSession), all Orders and Carts that belong to the `anonymousId` are assigned to the newly logged-in Customer.
- If the Customer does not have a Cart, the most recently modified anonymous cart becomes the Customer's Cart.
- If the Customer already has a Cart, the most recently modified anonymous cart is handled according to [AnonymousCartSignInMode](ctp:api:type:AnonymousCartSignInMode).
A Cart returned in the [CustomerSignInResult](ctp:api:type:CustomerSignInResult) has any invalid Line Items removed and is [updated](/api/carts-orders-overview#cart-updates) with the latest prices, taxes, and discounts. During these updates, the following errors can be returned: [MatchingPriceNotFound](ctp:api:type:MatchingPriceNotFoundError) and [MissingTaxRateForCountry](ctp:api:type:MissingTaxRateForCountryError).
If an account with the given credentials is not found, an [InvalidCredentials](ctp:api:type:InvalidCredentialsError) error is returned.
Retrieves the authenticated Customer (that matches the given email/password pair) if they are part of a specific Store.