to avoid circular references

[glynnbird]

Overview

When logging is enabled, nano would use JavaScript's clone operation so that it could scrub authentication credentials without actually deleting the originals. Instead, as suggested by issue #274 we just make a selective copy of certain attributes which avoids the possibility of a circular reference

Testing recommendations

See issue #274

GitHub issue number

Fixes issue #274

Checklist

• [x] Code is written and works correctly;
• [x] Changes are covered by tests;
• [x] Documentation reflects the changes;