Document default GPG key

[WilliamDEdwards]

Detailed Description

https://www.aptly.info/doc/aptly/publish/repo/ describes the -gpg-key="" flag as:

GPG key ID to use when signing the release, if not specified default key is used

However, I am unable to find what the 'default key' would be.

Additionally, the GpgKey at https://www.aptly.info/doc/api/publish/ does not state a default value. Is there one?

Context

Not knowing what the default key is could cause confusion.

Possible Implementation

N/A

Your Environment

N/A