Blocks a Device Add-In on a specific database. Clears any auto-enrollment configuration (including auto-enrollment groups), unenrolls every currently enrolled device, then sets the Add-In status to Blocked in MyGeotab and MyAdmin. Only reseller users can call this method. This is the same operation exposed by the L1 Device Add-In Management UI's "Block" action; it is intended for programmatic blocking without visiting the MyAdmin UI. Use UnblockAddIn to reverse this operation and restore the Add-In to the Active state. Idempotent: if the Add-In is already Blocked the call returns Success=true without re-issuing MyGeotab calls or unenrollment work.