Feature: Installation global config (#839) (#840)

* Renamed concern from Feature to Featurable

* Feature: Installation config (#839)
* Added new model installtion config with corresponding migrations and specs
* Created an installation config yml (key value store model)
* Created a config loader module to load the installaltion configs
* Added this to the config loader seeder
* Changed the account before create hook for default feature enabling to use the feature values from installtion config
* Renamed the feature concern to Featurable to follow the naming pattern for concerns
* Added comments and specs for modules and places that deemed necessary

* Refactored config loader to reduce cognitive complexity (#839)

db/migrate/20200510112339_create_installation_config.rb

@@ -0,0 +1,13 @@
+class CreateInstallationConfig < ActiveRecord::Migration[6.0]
+  def change
+    create_table :installation_configs do |t|
+      t.string :name, null: false
+      t.jsonb :serialized_value, null: false, default: '{}'
+      t.timestamps
+    end
+
+    add_index :installation_configs, [:name, :created_at], unique: true
+
+    ConfigLoader.new.process
+  end
+end