Feature: Knowledge Base APIs (#1002)

- Introduce models & migrations for portals, categories, folders and articles
- CRUD API for portals
- CRUD API for categories

Addresses: #714

Co-authored-by: Sojan <sojan@pepalo.com>

spec/factories/kbase/articles.rb

@@ -0,0 +1,14 @@
+FactoryBot.define do
+  factory :kbase_article, class: 'Kbase::Article' do
+    account_id { 1 }
+    category_id { 1 }
+    folder_id { 1 }
+    author_id { 1 }
+    title { 'MyString' }
+    content { 'MyText' }
+    status { 1 }
+    views { 1 }
+    seo_title { 'MyString' }
+    seo { '' }
+  end
+end