Log metadata from requests

What does this MR do?

This adds the meta.* fields from Labkit::Context to the logs for rails and the api.

This also avoids generating queries from our logs, meaning that in some cases the plan information would not be available.

Related to gitlab-com/gl-infra/scalability#68 (closed)

Examples

API:

{"time":"2020-05-06T10:38:19.368Z","severity":"INFO","duration_s":0.37849,"db_duration_s":0.02107,"view_duration_s":0.35742,"status":200,"method":"GET","path":"/api/v4/features","params":[],"host":"localhost","remote_ip":"127.0.0.1","ua":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:76.0) Gecko/20100101 Firefox/76.0","route":"/api/:version/features","queue_duration_s":20.927064,"redis_calls":14,"redis_duration_s":0.013014,"correlation_id":"VRBiQCqydA8","meta.user":"root","meta.caller_id":"/api/:version/features"}

Web:

{"method":"GET","path":"/","format":"html","controller":"RootController","action":"index","status":200,"time":"2020-05-06T09:31:00.039Z","params":[],"remote_ip":"127.0.0.1","user_id":1,"username":"root","ua":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:76.0) Gecko/20100101 Firefox/76.0","queue_duration_s":0.217213,"correlation_id":"2CKVdbsyca9","meta.user":"root","meta.caller_id":"RootController#index","gitaly_calls":13,"gitaly_duration_s":0.070923,"redis_calls":87,"redis_duration_s":0.155781,"cpu_s":15.14,"db_duration_s":0.09969,"view_duration_s":2.51219,"duration_s":11.46788}
{"method":"GET","path":"/-/peek/results","format":"json","controller":"Peek::ResultsController","action":"show","status":200,"time":"2020-05-06T09:31:03.241Z","params":[{"key":"request_id","value":"2CKVdbsyca9"}],"remote_ip":"127.0.0.1","user_id":1,"username":"root","ua":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:76.0) Gecko/20100101 Firefox/76.0","queue_duration_s":0.10111,"correlation_id":"qcBb6SxtE85","meta.user":"root","meta.caller_id":"Peek::ResultsController#show","redis_calls":5,"redis_duration_s":0.031849,"cpu_s":0.51,"db_duration_s":0.01487,"view_duration_s":0.00022,"duration_s":0.39572}

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done