magento#7366: GraphQl. subscribeEmailToNewsletter. Mutation for subsc…

…ribe feature.

src/guides/v2.4/graphql/mutations/subscribe-email-to-newsletter.md

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+---
+group: graphql
+title: subscribeEmailToNewsletter mutation
+contributor_name: Atwix
+contributor_link: https://www.atwix.com/
+---
+
+The `subscribeEmailToNewsletter` mutation allows subscription for guests and registered customers.
+
+## Syntax
+
+`mutation: {subscribeEmailToNewsletter(email: String!): SubscribeEmailToNewsletterOutput}`
+
+## Example usage
+
+The following call adds an email into a newsletter subscription.
+
+**Request:**
+
+```graphql
+mutation {
+  subscribeEmailToNewsletter(
+    email: "email@example.com"
+  ) {
+    status
+  }
+}
+```
+
+**Response:**
+
+```json
+{
+  "data": {
+    "subscribeEmailToNewsletter": {
+      "status": "SUBSCRIBED"
+    }
+  }
+}
+```
+
+## Input arguments
+
+Mutation contains a required `email` argument specified an email address which should be added into a newsletter subscription.
+
+## Output attributes
+
+The `SubscribeEmailToNewsletterOutput` object contains the following attributes:
+
+Attribute |  Data Type | Description
+--- | --- | ---
+`status` | SubscriptionStatusesEnum | Contains a subscription status of specified `email` address.
+
+### SubscriptionStatusesEnum object
+
+In general, the `SubscriptionStatusesEnum` object can return one of the following values:
+
+Value | Description
+--- | ---
+`NOT_ACTIVE` | Subscription requires a confirmation. Confirmation email has been sent to specified email address to confirm the subscription.
+`SUBSCRIBED` | Email address is subscribed.
+`UNSUBSCRIBED` | Email address is unsubscribed.
+`UNCONFIRMED` | Specified email ties to customer which did not confirm a required customer registration.
+
+For the `subscribeEmailToNewsletter` mutation the `SubscriptionStatusesEnum` object may return only 2 of them:
+
+- `NOT_ACTIVE`
+- `SUBSCRIBED`
+
+## Errors
+
+Error | Description
+--- | ---
+`Cannot create a newsletter subscription.` | General error message which appears on some internal system errors. The original error is logged and can be found in Magento logs.
+`Enter a valid email address.` | The value provided in the `email` argument has an invalid format.
+`Guests can not subscribe to the newsletter. You must create an account to subscribe.` | Guest subscription is disabled. Go to **Stores** > **Configuration** > **Customers** > **Newsletter** > **Subscription Options** > **Allow Guest Subscription** in the Admin to adjust the setting.
+`The account sign-in was incorrect or your account is disabled temporarily.` | The email address provided in the `email` argument ties to customer account pending confirmation.
+`This email address is already subscribed.` | The email address provided in the `email` argument is already subscribed.
+`You must specify an email address to subscribe to a newsletter.`| The empty value is provided in the `email` argument.