fix: fix primary key delimiter verificatoin step

docs: improve docs on unions

documentation/how_to/use-unions-with-graphql.md

@@ -1,6 +1,6 @@
 # Use Unions with GraphQL
 
-By default, if a union is used in your resource in line, it will get a nice type generated for it based on the 
+By default, if a union is used in your resource in line, it will get a nice type generated for it based on the
 resource/key name. Often, you'll want to define a union using `Ash.Type.NewType`. For example:
 
 ```elixir
@@ -21,6 +21,8 @@ defmodule MyApp.Armor do
     ]
   ]
 
+  use AshGraphql.Type
+
   # Add this to define the union in ash_graphql
   def graphql_type(_), do: :armor
 end
@@ -45,4 +47,4 @@ Which, in this case, would yield:
 
 ```
 type Armor = Plate | ChainMail | {custom: {value: String}}
-```
+```

lib/resource/resource.ex

@@ -360,14 +360,14 @@ defmodule AshGraphql.Resource do
   }
 
   @transformers [
-    AshGraphql.Resource.Transformers.RequirePkeyDelimiter,
     AshGraphql.Resource.Transformers.RequireKeysetForRelayQueries,
     AshGraphql.Resource.Transformers.ValidateActions,
     AshGraphql.Resource.Transformers.ValidateCompatibleNames
   ]
 
   @verifiers [
-    AshGraphql.Resource.Verifiers.VerifyQueryMetadata
+    AshGraphql.Resource.Verifiers.VerifyQueryMetadata,
+    AshGraphql.Resource.Verifiers.RequirePkeyDelimiter
   ]
 
   @sections [@graphql]

lib/resource/verifiers/require_pkey_delimiter.ex

@@ -0,0 +1,37 @@
+defmodule AshGraphql.Resource.Verifiers.RequirePkeyDelimiter do
+  # Ensures that the resource has a primary key called `id`
+  @moduledoc false
+
+  use Spark.Dsl.Verifier
+
+  alias Spark.Dsl.Verifier
+
+  def verify(dsl) do
+    if Verifier.get_persisted(dsl, :embedded?) do
+      :ok
+    else
+      primary_key =
+        dsl
+        |> Verifier.get_entities([:attributes])
+        |> Enum.filter(& &1.primary_key?)
+
+      case primary_key do
+        [_single] ->
+          :ok
+
+        [_ | _] ->
+          if Verifier.get_persisted(dsl, :primary_key) do
+            :ok
+          else
+            module = Verifier.get_persisted(dsl, :module)
+
+            raise Spark.Error.DslError,
+              module: module,
+              path: [:graphql, :primary_key_delimiter],
+              message:
+                "AshGraphql requires a `primary_key_delimiter` to be set for composite primary keys."
+          end
+      end
+    end
+  end
+end

lib/type.ex

@@ -3,6 +3,12 @@ defmodule AshGraphql.Type do
   Callbacks used to enrich types with GraphQL-specific metadata.
   """
 
+  defmacro __using__(_) do
+    quote do
+      @behaviour AshGraphql.Type
+    end
+  end
+
   @doc """
   Sets the name of the graphql type for a given Ash type. For example: `:weekday`.