Feat: add module ephemeral authorization handler

[moustachu]

Adding module for SMS ephemeral authorization

This pull request introduces a new SMS gateway integration for sending authentication codes, including a configurable service and localized message templates. The main changes are the addition of the SmsGatewayService, configuration options via environment variables, and new translations for SMS messages in multiple languages.

SMS Gateway Integration:

• Added a new Decidim::SmsGatewayService class to handle sending SMS authentication codes, supporting both Message Business and generic SMS providers. The service constructs requests based on configuration and uses localized messages. (app/services/decidim/sms_gateway_service.rb)
• Updated the Gemfile to include the decidim-ephemeral_authorization_handler dependency, which is required for the new SMS service. (Gemfile)

Configuration & Environment:

• Enhanced the decidim.rb initializer to allow SMS gateway service and its context (such as URL, credentials, and platform name) to be set via environment variables. (config/initializers/decidim.rb)

Localization:

• Added localized SMS message templates for authentication codes in English, French, German, and Dutch. (config/locales/en.yml, config/locales/fr.yml, config/locales/de.yml, config/locales/nl.yml) [1] [2] [3] [4]