This function is run once at the beginning of a session to
save credentials. The credentials list is referenced each
time an API call is sent, in order to create the proper
authentication header.Note that while the Shared Secret is input in plain text in
the R script and stored within an R session in a list, all
user credentials are hashed using the SHA1 algorithm and
converted to base64 as required by Adobe before making the
API call.
In order to access Reporting API, user must be part of the
"Web Service Access" user group (This is set in the Admin
panel).
When credentials are set properly, a message of
"Authentication succeeded" will be printed to the console.