Make GnuPG configuration closer to the duraconf one
_Originally created by @intrigeri on [#7512 (Redmine)](https://public-redmine-archive.tails.boum.org/code/issues/7512)_ We should make good use of the great work done on <https://help.riseup.net/en/security/message-security/openpgp/best-practices>. The example configuration file lives in <https://github.com/ioerror/duraconf.git>. Feature Branch: feature/7512-Make-GnuPG-config-closer-to-duraconf-reworked ### Related issues - **Blocks** tails/tails#7416
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