Migrate Azure Spring Apps backend to Azure Container Apps

[hemarina]

Azure Spring Apps is retired and this template needs to migrate its Java Spring Boot backend from Azure Spring Apps to Azure Container Apps.

This repository will be temporarily removed from the awesome-azd gallery while the migration is pending. After the migration is complete, feel free to submit a request to add the template back to the gallery.

Related references:

• Azure Spring Apps retirement guidance: https://aka.ms/asaretirement
• Gallery cleanup: ASA Sample no longer works Azure/awesome-azd#955

cc Pierre Malarme (@pmalarme) as you are one of the authors