Azure locking support implementation.

Digger is an open-source alternative to Terraform Cloud that enables running Terraform Plan and Apply in Github Actions.

The latest update adds Azure support for locking that can be implemented with Storage Account tables. It requires setting a mandatory environment variable of DIGGER_AZURE_AUTH_METHOD, which can take one of three values, and other variables depending on the authentication method used.

The motivation behind Digger is to provide specialized tools for managing Terraform's stateful nature to avoid race conditions while running multiple instances of code in different environments.