Loading DataFed Authz config file into Authz module - through env variable

[JoshuaSBrown]

Description

The DataFed authz module relies on a few configuration settings which are defined in a datafed-authz.conf file. There are two ways that the authz module can know where to look for the DataFed Authz config file.

1. Hard code it in the authz module as file path and place the path in a standard location
2. Load it into an env variable
3. When building the authz config module, use C++ Define statements to insert the configuration in directly.

Approach 1

Using a hard coded file path, this is brittle because it doesn't allow admins to change the location.
This is what is shown in the devel branch if no env variable is set. https://github.com/ORNL/DataFed/blob/devel/repository/gridftp/globus5/authz/AuthzWorker.cpp

Approach 2

Loading it into the gridftp service, requires editing the gridFTP service file and setting an env variable that points to the location of the authz config file.

Approach 3

Changing configuration would require rebuilding the C++ code from source.