improvement: add AshGraphql.Type

lib/type.ex

@@ -0,0 +1,63 @@
+defmodule AshGraphql.Type do
+  @moduledoc """
+  Callbacks used to enrich types with GraphQL-specific metadata.
+  """
+
+  @doc """
+  Sets the name of the graphql type for a given Ash type. For example: `:weekday`.
+
+  This will do different things depending on the type you're adding it to.
+
+  ## Regular Types
+
+  This expresses that you will define a custom type for representing this in your graphql
+
+  ## NewTypes
+  If it is a subtype of a union, or map/keyword with `fields` the type will be *created* with that name.
+  So you can use this to decide what it will be named. Otherwise, it behaves as stated above for
+  regular types.
+  """
+  @callback graphql_type(Ash.Type.constraints()) :: :atom
+
+  @doc """
+  Sets the name of the graphql input type for a given Ash type. For example: `:weekday`.
+
+  This will do different things depending on the type you're adding it to.
+
+  ## Regular Types
+
+  This expresses that you will define a custom type for representing this input in your graphql
+
+  ## NewTypes
+  If it is a subtype of a union, or map/keyword with `fields` the type will be *created* with that name.
+  So you can use this to decide what it will be named. Otherwise, it behaves as stated above for
+  regular types.
+  """
+  @callback graphql_input_type(Ash.Type.constraints()) :: :atom
+
+  @doc """
+  Used for `Ash.Type.Enum` to rename individual values. For example:
+
+  ```elixir
+  defmodule MyEnum do
+    use Ash.Type.Enum, values: [:foo, :bar, :baz]
+
+    def graphql_rename_value(:baz), do: :buz
+    def graphql_rename_value(other), do: other
+  end
+  ```
+  """
+  @callback graphql_rename_value(Ash.Type.constraints()) :: String.t() | :atom
+
+  @doc """
+  Used for map/embedded types embedded in unions, to avoid nesting them in a key by their name.
+
+  See [the unions guide](/documentation/how_to/use-unions-with-graphql.md) for more.
+  """
+  @callback graphql_unnested_unions(Ash.Type.constraints()) :: :atom
+
+  @optional_callbacks graphql_type: 1,
+                      graphql_input_type: 1,
+                      graphql_rename_value: 1,
+                      graphql_unnested_unions: 1
+end