Create restore-backups.md topic

[Andriciuc]

Add a new topic:

• How can I store an old key securely? Use Vault as an example here.
• Explain how you can use this “old” principal key to unencrypt your backups.

[Andriciuc]

Initial commit is related to a TOC fix, that has been bugging me for a while, next commits are related to decrypt

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.50%. Comparing base (8084e6a) to head (4f8b4b6).

❌ Your project status has failed because the head coverage (85.50%) is below the target coverage (90.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@                  Coverage Diff                  @@
##           TDE_REL_17_STABLE     #397      +/-   ##
=====================================================
- Coverage              85.51%   85.50%   -0.01%     
=====================================================
  Files                     22       22              
  Lines                   2547     2546       -1     
  Branches                 389      388       -1     
=====================================================
- Hits                    2178     2177       -1     
  Misses                   293      293              
  Partials                  76       76              

Components	Coverage Δ
access	83.73% <ø> (ø)
catalog	88.88% <ø> (ø)
common	91.80% <ø> (ø)
encryption	72.56% <ø> (ø)
keyring	72.94% <ø> (ø)
src	91.42% <ø> (ø)
smgr	94.85% <ø> (-0.03%)	⬇️
transam	∅ <ø> (∅)

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