Output semantic metadata to logs in JSON format

[mark-dce]

In order to easily leaverage search and filtering capabilities in log aggregation and analysis tools like AWS CloudWatch logs, we want to send our logs in an easily parsable format.

We've chosen Semantic Logger because it provides an easy drop-in replacement for the default Rails logger. Semantic Logger doesn't require us to change any of our existing logging code and makes it simple to output logs in JSON format.

[coveralls]

coverage: 93.368% (+0.02%) from 93.352% when pulling 409577198a3bfa1e2eeb739f6bda4270e86ed627 on semantic_logger into 8ec92fb6c92851a8fece0028153a861bdb95809d on main.