Q. Are the rules for the naming of Azure resources documented?
A. Yes. At https://docs.microsoft.com/en-us/azure/architecture/best-practices/naming-conventions#naming-rules-and-restrictions all the rules and restrictions for naming of Azure resources are listed. It is a good idea to create a naming convention for your resources that adhere to these rules and restrictions. This will avoid the chance of any deployments failing due to bad naming.