Add custom logging hooks

[nicola88]

As discussed in the linked issue, I updated the documentation and tests to customize Pino hooks and intercept and manipulate logging arguments, which will be used for audit logs.

The current version of lc39 already allows to pass the custom hook in the hooks field of the Pino logger options, so no specific change was required.

Checklist

• your branch will not cause merge conflict with master
• run npm test
• tests are included
• the documentation is updated or integrated 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]

LGTM