Add Notion to the list of supported providers

src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationHandlers.Userinfo.cs

@@ -64,9 +64,16 @@ public static partial class OpenIddictClientWebIntegrationHandlers
                 var request = context.Transaction.GetHttpRequestMessage() ??
                     throw new InvalidOperationException(SR.GetResourceString(SR.ID0173));
 
+                // Notion requires sending an explicit API version (which is statically set
+                // to the last version known to be supported by the OpenIddict integration).
+                if (context.Registration.ProviderType is ProviderTypes.Notion)
+                {
+                    request.Headers.Add("Notion-Version", "2022-06-28");
+                }
+
                 // Trakt requires sending both an API key (which is always the client identifier) and an API version
                 // (which is statically set to the last version known to be supported by the OpenIddict integration).
-                if (context.Registration.ProviderType is ProviderTypes.Trakt)
+                else if (context.Registration.ProviderType is ProviderTypes.Trakt)
                 {
                     request.Headers.Add("trakt-api-key", context.Registration.ClientId);
                     request.Headers.Add("trakt-api-version", "2");

src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationProviders.xml

@@ -588,6 +588,25 @@
     </Environment>
   </Provider>
 
+  <!--
+                                          ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄
+                                          ██ ▀██ ██ ▄▄▄ █▄▄ ▄▄█▄ ▄██ ▄▄▄ ██ ▀██ ██
+                                          ██ █ █ ██ ███ ███ ████ ███ ███ ██ █ █ ██
+                                          ██ ██▄ ██ ▀▀▀ ███ ███▀ ▀██ ▀▀▀ ██ ██▄ ██
+                                          ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
+  -->
+
+  <Provider Name="Notion" Id="8ed2d19d-bd97-4121-a3b1-61b6732c9cdd"
+            Documentation="https://developers.notion.com/docs/authorization">
+    <Environment Issuer="https://www.notion.com/">
+      <Configuration AuthorizationEndpoint="https://api.notion.com/v1/oauth/authorize"
+                     TokenEndpoint="https://api.notion.com/v1/oauth/token"
+                     UserinfoEndpoint="https://api.notion.com/v1/users/me">
+        <TokenEndpointAuthMethod Value="client_secret_basic" />
+      </Configuration>
+    </Environment>
+  </Provider>
+
   <!--
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                                         ██ ▄▄ █ ▄▄▀█▄▄ ▄▄██ ▄▄▀██ ▄▄▄██ ▄▄▄ ██ ▀██ ██