Write action log to support technical audits

[fwaibel]

As a system administrator I'd like to know what happened on a stackable 'managed' node.

An action log containing the relevant actions performed by the agent could help maintaining a comprehensible state of the nodes.

• downloaded version x.y.z of software abc
• extracted software abc version x.y.z into folder foo
• applied default security configuration
• started node as part of a cluster ...
• downloaded security patch x.y.z+1 of software abc
• removed node from running cluster
• stopped node
• started rolling update of node 3 of cluster
• added node to running cluster
• rolling update finished successfully ...
• download new major version x+1.0.0 of software abc
• applied configuration migration
• started stop-the-world cluster update ...

[soenkeliebau]

idea: if we enforce criteria for our log levels we could say "filter the log for [INFO] messages and this will be the equivalent of an action log"