feat(logging): support custom time, level and message keys

[GeorgeMac]

Fixes FLI-148
Fixes #1252

Adds support for custom keys in log output for:

• time
• level
• message

Each key can be configured under the log.keys object in the configuration.

Using the following Flipt configuration I get the subsequent logging output format:

config.yaml:

log:
  level: DEBUG
  encoding: json
  keys:
    time: "time"
    level: "level"
    message: "msg"

Flipt output:

{"level":"INFO","time":"2023-01-27T12:39:30Z","msg":"flipt starting","version":"dev","commit":"","date":"","go_version":"go1.19.5"}
{"level":"DEBUG","time":"2023-01-27T12:39:30Z","msg":"not a release version, disabling telemetry"}
{"level":"DEBUG","time":"2023-01-27T12:39:30Z","msg":"local state directory exists","path":"/Users/georgemac/Library/Application Support/flipt"}
{"level":"DEBUG","time":"2023-01-27T12:39:30Z","msg":"using driver","driver":"sqlite3"}
{"level":"DEBUG","time":"2023-01-27T12:39:30Z","msg":"migrations up to date"}
{"level":"DEBUG","time":"2023-01-27T12:39:30Z","msg":"store enabled","server":"grpc","driver":"sqlite3"}
{"level":"DEBUG","time":"2023-01-27T12:39:30Z","msg":"authentication method \"token\" server registered","server":"grpc"}
{"level":"DEBUG","time":"2023-01-27T12:39:30Z","msg":"authentication method \"oidc\" server registered","server":"grpc"}
{"level":"INFO","time":"2023-01-27T12:39:30Z","msg":"authentication middleware enabled","server":"grpc"}
{"level":"INFO","time":"2023-01-27T12:39:30Z","msg":"cleanup process not acquired","server":"grpc","next_attempt":"2023-01-27T12:49:10Z"}
{"level":"DEBUG","time":"2023-01-27T12:39:30Z","msg":"starting grpc server","server":"grpc"}
{"level":"INFO","time":"2023-01-27T12:39:30Z","msg":"CORS enabled","server":"http","allowed_origins":["http://localhost:5173","http://localhost:8080"]}
{"level":"DEBUG","time":"2023-01-27T12:39:30Z","msg":"starting http server","server":"http"}
{"level":"INFO","time":"2023-01-27T12:39:30Z","msg":"api available","server":"http","address":"http://0.0.0.0:8080/api/v1"}
{"level":"INFO","time":"2023-01-27T12:39:30Z","msg":"ui available","server":"http","address":"http://0.0.0.0:8080"}

[codecov-commenter]

Codecov Report

Merging #1295 (21f3929) into main (9eef7e5) will increase coverage by 0.03%.
The diff coverage is 100.00%.

📣 This organization is not using Codecov’s GitHub App Integration. We recommend you install it so Codecov can continue to function properly for your repositories. Learn more

@@            Coverage Diff             @@
##             main    #1295      +/-   ##
==========================================
+ Coverage   79.88%   79.92%   +0.03%     
==========================================
  Files          43       43              
  Lines        3267     3272       +5     
==========================================
+ Hits         2610     2615       +5     
  Misses        527      527              
  Partials      130      130              

Impacted Files	Coverage Δ
internal/config/log.go	100.00% <100.00%> (ø)

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[markphelps]

♥️it! lets verify with @giddel that it would fix their issue/usecase in #1252 and also queue up a docs update PR for the new config keys!

🤩

[GeorgeMac]

Added the associated docs PR here flipt-io/docs#24