Set `default_granularity` in `SetDefaultGranularityRule`

[courtneyholcomb]

Description

Actually set the default_granularity during transformation using SetDefaultGranularityRule. This was an oversight from a previous PR. I added a test this time to ensure it works.

Checklist

• [x] I have read the contributing guide and understand what's expected of me
• [x] I have signed the CLA
• [x] This PR includes tests, or tests are not required/relevant for this PR
• [ ] I have run changie new to create a changelog entry