Log guidelines improvements

[fredmaggiowski]

Checklist

• your branch will not cause merge conflict with master
• run npm test
• tests are included
• the documentation is updated or intregrated accordingly with your changes
• the code will follow the lint rules and style of the project
• you are not committing extraneous files or sensible data

[fredmaggiowski]

Log samples

{"level":30,"time":57521674.786215,"pid":42380,"hostname":"mycomputer","msg":"Server listening at http://0.0.0.0:61625","v":1}
{"level":30,"time":57521677.424422,"pid":42380,"hostname":"mycomputer","reqId":1,"http":{"request":{"method":"GET"}},"url":{"full":"/"},"userAgent":{},"host":{"ip":"127.0.0.1"},"msg":"incoming request","v":1}
{"level":30,"time":57521677.863477,"pid":42380,"hostname":"mycomputer","reqId":1,"http":{"response":{"statusCode":200,"body":{}}},"responseTime":0.4573419988155365,"msg":"request completed","v":1}

[allevo]

We lost an error log with this.

[fredmaggiowski]

You mean this one?

https://github.com/fastify/fastify/blob/667d4644eab09f27bc30cad6e7378f5fc82cb9e8/lib/reply.js#L587

In that case it's intended to be disabled: fastify/fastify#2319