Verify (and Document?) Additional Software Feature behaviour with apt-key

Hi,

Additionnal Software feature documents how to add a repository here https://tails.boum.org/doc/advanced_topics/additional_software/index.en.html.
However, lot of those repositories use additionnal PGP keys for integrity etc.

As the documentation does not mention anything about those keys and their use, I am wondering,

- How/If it will work without those keys
- If/How it won’t be wortly to document how to add those keys, if douable.

Original created by @geb on 15626 (Redmine)

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