[feature + performance] add JSON logging format (#4355)

# Description

Adds JSON logging as an optional alternative log output format. In the process this moves our log formatting itself into a separate subpkg to make it more easily modular, and improves caller name getting with some calling function name caching.

## Checklist

- [x] I/we have read the [GoToSocial contribution guidelines](https://codeberg.org/superseriousbusiness/gotosocial/src/branch/main/CONTRIBUTING.md).
- [x] I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
- [x] I/we have not leveraged AI to create the proposed changes.
- [x] I/we have performed a self-review of added code.
- [x] I/we have written code that is legible and maintainable by others.
- [x] I/we have commented the added code, particularly in hard-to-understand areas.
- [x] I/we have made any necessary changes to documentation.
- [ ] I/we have added tests that cover new code.
- [x] I/we have run tests and they pass locally with the changes.
- [x] I/we have run `go fmt ./...` and `golangci-lint run`.

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4355
Co-authored-by: kim <grufwub@gmail.com>
Co-committed-by: kim <grufwub@gmail.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/internal/config/defaults.go b/internal/config/defaults.go
index 1540cc76b..df3b64b40 100644
--- a/internal/config/defaults.go
+++ b/internal/config/defaults.go
@@ -29,6 +29,7 @@ import (
 // if you use this, you will still need to set Host, and, if desired, ConfigPath.
 var Defaults = Configuration{
 	LogLevel:           "info",
+	LogFormat:          "logfmt",
 	LogTimestampFormat: "02/01/2006 15:04:05.000",
 	LogDbQueries:       false,
 	ApplicationName:    "gotosocial",