Implement loading settings from both, database and env variables [SCI-8813] (#5885)

app/models/application_settings.rb

@@ -1,4 +1,7 @@
 # frozen_string_literal: true
 
 class ApplicationSettings < Settings
+  def load_values_from_env
+    ENV.select { |name, _| name =~ /^APP_STTG_[A-Z0-9_]*/ }.transform_keys(&:downcase)
+  end
 end

app/models/settings.rb

@@ -4,4 +4,16 @@ class Settings < ApplicationRecord
   def self.instance
     first || new
   end
+
+  def values
+    merged_values = super
+    self.class.instance_methods(false).grep(/^load_values_from_[A-Z0-9_]*/).each do |method|
+      merged_values = merged_values.merge(public_send(method))
+    end
+    merged_values
+  end
+
+  def load_values_from_env
+    raise NotImplementedError
+  end
 end