feat: Add Sendethics possibility to the sms gateway

[AyakorK]

🎩 Description

This adds the possibility of sending messages through Sendethics api which has a different behaviour from previous providers like ÉtoileDièse or Twilio

📌 Related Issues

Link your PR to an issue

• Decidim-app - Ajout SMS Gateway with Sendethics

Testing

Describe the best way to test or validate your PR.

Creation of the Instance

• Create a .env
• Fill in those data (Please note that you can test both of Sendethics or [Twilio, EtoileDièse] depending what you need to test there

# SENDETHICS 
SMS_GATEWAY_MB_API_KEY=<your_api_key>
SMS_GATEWAY_MB_ACCOUNT_ID=<your_account_id>

# ETOILEDIESE OR TWILIO
SMS_GATEWAY_USERNAME=<username_on_provider>
SMS_GATEWAY_PASSWORD=<password_on_provider>

# GLOBAL ENV VARS
SMS_GATEWAY_SERVICE="Decidim::SmsGatewayService" # Mandatory to be this one
SMS_GATEWAY_URL="<url_to_use>" # Please make sure this does not end with a "/" otherwise it will cause errors

• Setup your app

🚨 If you have to change your .env you'll need to restart your app to apply changes !

Example:

• Log in as admin
• Access Backoffice
• Go to organization settings
• Go to authentication settings
• Enable authentication using SMS
• Go to participatory processes
• Access participatory process
• Access settings from a budget component
• Make sure you can vote without the zipcode (otherwise won't work)
• Go to front office
• Access the budget and try to vote
• Fill in your phone number and try to send the SMS
• Make sure you receive the message on your phone

Tasks

• Add specs
• Add env vars
• Modify the service to add the behavior from Sendethics

📷 Screenshots

Please add screenshots of the changes you're proposing if related to the UI

[Quentinchampenois]

I will continue this PR

[Quentinchampenois]

Prefer to define a dedicated class implementing an interface SmsGateway with method request callable rather than if / else condition

[moustachu]

Refactor later 🕐