Recovery support: Or how to tame secret storage and backups

[poljar]

This PR implements a Recovery API. This API or subsystem attempts to unify the backup and secret storage support into a single and simplified API.

This Recovery API is also what Element X uses for their backup and secret storage support.

[poljar]

Not actually ready for review, but want to get the CI going.

[codecov]

Codecov Report

Attention: 32 lines in your changes are missing coverage. Please review.

Comparison is base (05f0106) 82.64% compared to head (1b492ae) 82.65%.
Report is 1 commits behind head on main.

❗ Current head 1b492ae differs from pull request most recent head 0937934. Consider uploading reports for the commit 0937934 to get more accurate results

Files	Patch %	Lines
...ates/matrix-sdk/src/encryption/recovery/futures.rs	76.25%	19 Missing ⚠️
crates/matrix-sdk/src/encryption/recovery/mod.rs	84.33%	13 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #2842    +/-   ##
========================================
  Coverage   82.64%   82.65%            
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  Files         216      219     +3     
  Lines       22183    22354   +171     
========================================
+ Hits        18333    18476   +143     
- Misses       3850     3878    +28     

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[poljar]

This is now ready for review. cc @jplatte

[bertybuttface]

Is there an example of how to use this recovery API?

[Hywan]

You can check the documentation which contains examples, https://matrix-org.github.io/matrix-rust-sdk/matrix_sdk/encryption/recovery/index.html.

[bertybuttface]

~~Thanks for replying but is this not different?

This PR seems to be adding a new convenience API which that example does not.~~

Scratch that, there are examples in the docs just not in the code repository examples folder.