feat: notion OAuth setup (#11765)

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

spec/controllers/concerns/notion_concern_spec.rb

@@ -0,0 +1,56 @@
+require 'rails_helper'
+
+RSpec.describe NotionConcern, type: :concern do
+  let(:controller_class) do
+    Class.new do
+      include NotionConcern
+    end
+  end
+
+  let(:controller) { controller_class.new }
+
+  describe '#notion_client' do
+    let(:client_id) { 'test_notion_client_id' }
+    let(:client_secret) { 'test_notion_client_secret' }
+
+    before do
+      allow(GlobalConfigService).to receive(:load).with('NOTION_CLIENT_ID', nil).and_return(client_id)
+      allow(GlobalConfigService).to receive(:load).with('NOTION_CLIENT_SECRET', nil).and_return(client_secret)
+    end
+
+    it 'creates OAuth2 client with correct configuration' do
+      expect(OAuth2::Client).to receive(:new).with(
+        client_id,
+        client_secret,
+        {
+          site: 'https://api.notion.com',
+          authorize_url: 'https://api.notion.com/v1/oauth/authorize',
+          token_url: 'https://api.notion.com/v1/oauth/token',
+          auth_scheme: :basic_auth
+        }
+      )
+
+      controller.notion_client
+    end
+
+    it 'loads client credentials from GlobalConfigService' do
+      expect(GlobalConfigService).to receive(:load).with('NOTION_CLIENT_ID', nil)
+      expect(GlobalConfigService).to receive(:load).with('NOTION_CLIENT_SECRET', nil)
+
+      controller.notion_client
+    end
+
+    it 'returns OAuth2::Client instance' do
+      client = controller.notion_client
+      expect(client).to be_an_instance_of(OAuth2::Client)
+    end
+
+    it 'configures client with Notion-specific endpoints' do
+      client = controller.notion_client
+      expect(client.site).to eq('https://api.notion.com')
+      expect(client.options[:authorize_url]).to eq('https://api.notion.com/v1/oauth/authorize')
+      expect(client.options[:token_url]).to eq('https://api.notion.com/v1/oauth/token')
+      expect(client.options[:auth_scheme]).to eq(:basic_auth)
+    end
+  end
+end