fix: issues with OIDC strategy (#800)

* Make OIDC dsl available

* Fix OIDC configuration validation.

Assent uses strings for the client_authentication_method. Therefore
changed the DSL to use string as well, in stead of atoms.

* Set correct provider for OIDC

lib/ash_authentication/strategies/oidc.ex

@@ -54,6 +54,8 @@ defmodule AshAuthentication.Strategy.Oidc do
   alias AshAuthentication.Strategy.{Custom, Oidc}
   use Custom, entity: Dsl.dsl()
 
+  @doc false
+  defdelegate dsl, to: Dsl
   defdelegate transform(strategy, dsl_state), to: Oidc.Transformer
   defdelegate verify(strategy, dsl_state), to: Oidc.Verifier
 end

lib/ash_authentication/strategies/oidc/dsl.ex

@@ -42,8 +42,8 @@ defmodule AshAuthentication.Strategy.Oidc.Dsl do
       ],
       client_authentication_method: [
         type:
-          {:in, [:client_secret_basic, :client_secret_post, :client_secret_jwt, :private_key_jwt]},
-        default: :client_secret_basic,
+          {:in, ["client_secret_basic", "client_secret_post", "client_secret_jwt", "private_key_jwt"]},
+        default: "client_secret_basic",
         doc: "The client authentication method to use.",
         required: false
       ],

lib/ash_authentication/strategies/oidc/transformer.ex

@@ -13,6 +13,7 @@ defmodule AshAuthentication.Strategy.Oidc.Transformer do
   def transform(strategy, dsl_state) when strategy.nonce == true do
     strategy
     |> Map.put(:nonce, {NonceGenerator, []})
+    |> Map.put(:provider, :oidc)
     |> OAuth2.transform(dsl_state)
   end