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>

db/migrate/20200704140509_create_kbase_articles.rb

@@ -0,0 +1,18 @@
+class CreateKbaseArticles < ActiveRecord::Migration[6.0]
+  def change
+    create_table :kbase_articles do |t|
+      t.integer :account_id, null: false
+      t.integer :portal_id, null: false
+      t.integer :category_id
+      t.integer :folder_id
+      t.integer :author_id
+      t.string :title
+      t.text :description
+      t.text :content
+      t.integer :status
+      t.integer :views
+
+      t.timestamps
+    end
+  end
+end