Experiment Metric Override Entry
Per-metric analysis overrides stored on the experiment (matches internal metricOverrides).
ID of the metric to override settings for.
Available options:
conversion, lookback, Must be true for the override to take effect. If true, the other proper prior settings in this object will be used if present.
Must be true for the override to take effect. If true, the other regression adjustment settings in this object will be used if present.

