Default connection configuration

[josegrobles]

Currently you need to specify explicitly the connection key for the configuration, in my opinion it should not be mandatory and it should default to the AZURE_SERVICEBUS_CONNECTION_STRING environment variable

[feliun]

@josegrobles generally I prefer configuration to be agnostic of the implementation. Azure relies on process.env, which is not a great practice IMO. I prefer to abstract that away and leave the client hardcode the string, or provide the process.env:

connectionString: "whateverIlike" || process.env. AZURE_SERVICEBUS_CONNECTION_STRING