Add error handling middleware

[Lutherwaves]

I actually found a useful existing Issue in Go Chi which might point me in the right direction for wrapping a wholesale error handler - https://github.com/go-chi/chi/issues/914

[Lutherwaves]

Updates:

• GO down the handlerfunction path https://github.com/tink3rlabs/example-app/blob/main/pkg/httputil/httputil.go#L82
• Keep separate from Validation logic
• Chain-wrap methods in the Router
• Align on terminology (rename middleware.Validator to handler.Validator)

@ayashjorden ^^^