PlanningCenterClient Expects Basic Auth Already Base64 Encoded

[onairmarc]

Describe The Issue

The PlanningCenterClient expects the Basic Auth App ID and App Secret to be already base64 encoded. PCO does not deliver this value as the SDK currently expects.

Describe the Expected Behavior

The PlanningCenterClient should perform the Base64 encoding itself. The only change should be that instead of providing an already Base64 encoded value, you provide APP_ID:APP_SECRET and the PlanningCenterClient handles the encoding itself.