Log output configuration options

[jrauschenbusch]

Describe the feature

The log level of mittens should be configurable via cli argument: e.g. trace, debug, info, warn, error, fatal, panic

The log format should be configurable via cli argument: e.g. text, json

The date time format of logs should be configurable: e.g. iso8601 , rfc3339, epoch

Rational

For production use cases it can be required to have more control over the generated log output.

Example Scenario

Kubernetes workloads and autoscaling: each time a new pod is created and mittens starts to warm the target container it produces a lot of non-essential logs. Furthermore the logs are in their own format so that it's hard to index them in a centralized log mgmt system.