Add endTrial method and document billing anchor

Author: driesvints

README.md

@@ -543,6 +543,18 @@ $user = User::find(1);
 $user->subscription()->noProrate()->swap('product-id', 'variant-id');
 ```
 
+### Changing The Billing Date
+
+To change the date of the month on which your customer gets billed for their subscription, you may use the `anchorBillingCycleOn` method:
+
+```php
+$user = User::find(1);
+
+$user->subscription()->anchorBillingCycleOn(21);
+```
+
+In the above example, the customer will now get billed on the 21st of each month going forward. For more info, see [the Lemon Squeezy docs](https://docs.lemonsqueezy.com/guides/developer-guide/managing-subscriptions#changing-the-billing-date).
+
 ### Multiple Subscriptions
 
 In some situation you may find yourself wanting to allow your customer to subscribe to multiple subscription types. For example, a gym may offer a swimming and weight lifting subscription. You can allow your customer to subscribe to either or both.
@@ -732,6 +744,18 @@ if ($user->subscription()->hasExpiredTrial()) {
 }
 ```
 
+##### Ending Trials Early
+
+To end a trial with payment upfront early you may use the `endTrial` method on a subscription:
+
+```php
+$user = User::find(1);
+
+$user->subscription()->endTrial();
+```
+
+This method will move the billing achor to the current day and thus ending any trial period the customer had.
+
 ## Handling Webhooks
 
 Lemon Squeezy can send your app webhooks which you can react on. By default, this package alread does the bulk of the work for you. [If you've properly set up webhooks](#webhooks), it'll listen to any incoming events and update your database accordingly. We recommend enabling all event types so it's easy for you to upgrade in the future.

src/Subscription.php

@@ -254,6 +254,14 @@ public function anchorBillingCycleOn(?int $date): self
         return $this;
     }
 
+    /**
+     * End the current trial by resetting the billing anchor to today.
+     */
+    public function endTrial(): self
+    {
+        return $this->anchorBillingCycleOn(0);
+    }
+
     /**
      * Swap the subscription to a new product plan.
      */