Update our OpenPGP keys in 2015

Originally created by @sajolida on #10012 (Redmine)

What we’re supposed to do each year:

1. Add a “Tails developers <tails@boum.org>” UID without comment to our signing key: https://www.debian-administration.org/users/dkg/weblog/97
2. Bump the signing key’s expiration date by 1 year, that is to next January 11.
3. Generate a new signing subkey for each RM, and move it onto their smartcards.
4. Shall we generate and split a revocation certificate for our signing key? See proposal in (https://gitlab.tails.boum.org/tails/private/-/issues/7700#note_99418).

To be done at the CI sprint in September.

Subtasks

• tails/tails#10013
• tails/tails#10014
• tails/tails#10016
• tails/tails#10019
• tails/sysadmin#10020

Related issues

• Related to #11572 (closed)