Investigate use of Virtual network and private endpoints for Cosmos

[jongio]

No description provided.

[rajeshkamal5050]

@weikanglim thinking that some of the exploration on issue #1142 might result in

• Configuring vnets and private endpoints for our template DB's @mcollier had some of the vnet bicep modules - https://github.com/Azure-Samples/virtual-network-integration-recipes adding for reference.
• Do you think APIM gateway could help privatize DB's for both local and production use-cases? keeping provisioning/IaC bicep same for local and production.

cc: @jongio

[rajeshkamal5050]

Changed #1142 issue desc to handle for all templates and its DB's i.e., Cosmos and Azure SQL. Marking this as a duplicate of #1142