Change DAL from SQL Server to Azure Cosmos DB SQL API

[EliuX]

We are moving away from the Azure SQL database serverless to embrace Azure Cosmos DB SQL API (To know more, please check out the Slack channel). We want to move from the current working solution of the DAL to one that uses the library azure-cosmos. The current design should let do this just by changing the classes related to SQL Alchemy. After we finish these changes we would have verified that the current architecture and design are solid and we move from here to replace the whole database model for a new model.