Gologshim runtime controlled handler

[MarcoPolo]

lidel, take a look and let me know your thoughts. This is targeting your branch.

This removes the goLogBridge interface check and having to modify the default slog logger. Instead you explicitly set the handler via gologshim.SetDefaultHandler.

[gammazero]

I think this makes the code cleaner/clearer. Your call @lidel

[lidel]

This works for us also, pushed docs + some thoughts below:

On the trade-off here

Original #3418 required no changes in existing apps, just updating both go-log and go-libp2p to latest versions.

This PR requires every legacy application that used both go-log and go-libp2p to add this extra code:

  import (
      logging "github.com/ipfs/go-log/v2"
      "github.com/libp2p/go-libp2p/gologshim"
  )

  func init() {
      // After go-log's init() runs and installs slog bridge,
      // tell gologshim to use it      
      handler := slog.Default().Handler()      
      // Verify it's go-log's bridge
      type goLogBridge interface {
	      GoLogBridge()
      }
      if _, ok := handler.(goLogBridge); !ok {
	      panic("aborting startup: slog.Default() is not go-log's bridge, logs would be missing due to incorrect wiring")
      }
      // use the go-log bridge      
      gologshim.SetDefaultHandler(handler)
  }

If this is the price to pay to fix logs, we can do the above in Kubo, Rainbow and every other application Shipyard maintains, but everyone else will be missing logs unless they do the same.

Just a trade-off decision.

Next steps

@MarcoPolo lgtm, i've tested this PR in ipfs/kubo#11039 and it also works for us (with the above extra code).

Up to you if you prefer implicit or explicit.

• If you prefer explicit, feel free to merge this PR into #3418, and then merge that (#3419+#3418).
• If you are ok with implicit detection, this PR can be closed and only merge #3418

Either way, we would appreciate a release with a fix 🙏