types/logger: add AsJSON

Printing out JSON representation things in log output is pretty common.

Updates #cleanup

Change-Id: Ife2d2e321a18e6e1185efa8b699a23061ac5e5a4
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f