As a developer, I'd like to simplify the API models by removing UOM, so that it is simpler and more consistent.

Done Criteria

• UOM is no longer referenced in swatch openapi definitions
• Automation tests are no longer referencing UOM
• UOM is no longer referenced in SWatch code
• UOM is no longer stored as part of events. 
• Double check that no queries are using UOM
• Swatch  check swatch-support-scripts repo to make sure UOM Is no longer referenced: https://gitlab.cee.redhat.com/rhsm/swatch-support-scripts/-/merge_requests/14
• check bin/ scripts to make sure UOM is no longer referenced
• FloorPlan exports that expose the metric_id column as UOM & metric_id can stay the same