Allow `destroy` routes to point at `update` actions.

**Is your feature request related to a problem? Please describe.**
My resource has the following update action:

```elixir
update :close do
change set_attribute(:status, "closed")
end
```

When exposing it via JSON:API I think the most reasonable thing to do is expose it as a `DELETE` endpoint.

**Describe the solution you'd like**
Allow `delete` route entities to accept update actions in addition to destroy and generic actions.

**Describe alternatives you've considered**

```elixir
routes do
base "/tickets"
patch :close, route: "/:id/close"
end
```

**Express the feature either with a change to resource syntax, or with a change to the resource interface**

```elixir
routes do
base "/tickets"
delete :close
end
```

**Additional context**
🐚

Locate the JSON:API route handling for delete entities and the validation that limits them to destroy or generic actions. Confirm that a `delete :close` declaration accepts the update action and verify the route invokes it with the expected DELETE behavior.

Written by the indexing model from the issue text.