Add support for premium app integrations

Co-authored-by: Danny <1695103+Rapptz@users.noreply.github.com>
Co-authored-by: Lucas Hardt <lucas.hardt@fu-berlin.de>
Co-authored-by: Andrin S. <65789180+Puncher1@users.noreply.github.com>

docs/api.rst

@@ -496,6 +496,47 @@ Debug
     :type payload: Union[:class:`bytes`, :class:`str`]
 
 
+Entitlements
+~~~~~~~~~~~~
+
+.. function:: on_entitlement_create(entitlement)
+
+    Called when a user subscribes to a SKU.
+
+    .. versionadded:: 2.4
+
+    :param entitlement: The entitlement that was created.
+    :type entitlement: :class:`Entitlement`
+
+.. function:: on_entitlement_update(entitlement)
+
+    Called when a user updates their subscription to a SKU. This is usually called when
+    the user renews or cancels their subscription.
+
+    .. versionadded:: 2.4
+
+    :param entitlement: The entitlement that was updated.
+    :type entitlement: :class:`Entitlement`
+
+.. function:: on_entitlement_delete(entitlement)
+
+    Called when a users subscription to a SKU is cancelled. This is typically only called when:
+
+    - Discord issues a refund for the subscription.
+    - Discord removes an entitlement from a user.
+
+    .. warning::
+
+        This event won't be called if the user cancels their subscription manually, instead
+        :func:`on_entitlement_update` will be called with :attr:`Entitlement.ends_at` set to the end of the
+        current billing period.
+
+    .. versionadded:: 2.4
+
+    :param entitlement: The entitlement that was deleted.
+    :type entitlement: :class:`Entitlement`
+
+
 Gateway
 ~~~~~~~~
 
@@ -3429,6 +3470,47 @@ of :class:`enum.Enum`.
         The underlying type of the ID is a channel or thread.
 
 
+.. class:: SKUType
+
+    Represents the type of a SKU.
+
+    .. versionadded:: 2.4
+
+    .. attribute:: subscription
+
+        The SKU is a recurring subscription.
+
+    .. attribute:: subscription_group
+
+        The SKU is a system-generated group which is created for each :attr:`SKUType.subscription`.
+
+
+.. class:: EntitlementType
+
+    Represents the type of an entitlement.
+
+    .. versionadded:: 2.4
+
+    .. attribute:: application_subscription
+
+        The entitlement was purchased as an app subscription.
+
+
+.. class:: EntitlementOwnerType
+
+    Represents the type of an entitlement owner.
+
+    .. versionadded:: 2.4
+
+    .. attribute:: guild
+
+        The entitlement owner is a guild.
+
+    .. attribute:: user
+
+            The entitlement owner is a user.
+
+
 .. _discord-api-audit-logs:
 
 Audit Log Data
@@ -4714,6 +4796,30 @@ ShardInfo
 .. autoclass:: ShardInfo()
     :members:
 
+SKU
+~~~~~~~~~~~
+
+.. attributetable:: SKU
+
+.. autoclass:: SKU()
+    :members:
+
+SKUFlags
+~~~~~~~~~~~
+
+.. attributetable:: SKUFlags
+
+.. autoclass:: SKUFlags()
+    :members:
+
+Entitlement
+~~~~~~~~~~~
+
+.. attributetable:: Entitlement
+
+.. autoclass:: Entitlement()
+    :members:
+
 RawMessageDeleteEvent
 ~~~~~~~~~~~~~~~~~~~~~~~