Werk #11127: azure_ad: Add counter metric

Component	Checks & agents
Title	azure_ad: Add counter metric
Date	May 14, 2020
Level	Trivial Change
Class	New Feature
Compatibility	Compatible - no manual interaction needed
Checkmk versions & editions	2.0.0i1 Checkmk Community, Checkmk Pro, Checkmk Ultimate MT

Added metric to visualize the amount of user accounts with a graph.

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