Add further details on simple development sandbox

Added a note that one can add a username used in basic auth
that mocks up what the Shibboleth SP or other authentication module
will populate into REMOTE_USER.

docs/simple-development.md

@@ -181,14 +181,24 @@ Restart the services and you can now authenticate to COmanage Registry
 using the username and password combination you added to the password
 file.
 
+Note that an authentication module used in production, like the 
+Shibboleth Service Provider (SP), often sets the "username" to a
+more sophisticated value. For example, if the Shibboleth SP is configured
+to consume eduPersonPrincipalName (ePPN) and populate that into
+`REMOTE_USER` then the "username" might be a value like
+`scott.koranda@uwm.edu`. 
+
+You can mock up the same behavior by simply adding the "username"
+`scott.koranda@uwm.edu` with a password using the above technique.
+
 ### Mocking Apache CGI environment variables
 
 Some COmanage Registry functionality, such as the
 [Env Source](https://spaces.at.internet2.edu/x/swr9Bg)
 Organizational Identity Source, requires that the Apache HTTP Server
 set Apache CGI environment variables. These environment variables are
 usually set by more sophisticated authentication modules like the
-Shibboleth Service Provider (SP). You can mock up the same 
+Shibboleth (SP). You can mock up the same 
 behavior using the
 [SetEnv](https://httpd.apache.org/docs/2.4/mod/mod_env.html)
 directive for Apache.