fix: sanitize permissions

[RiccardoM]

Description

This PR adds permissions sanitation before storing the permissions while handling a MsgSetUserGroupPermissions or MsgSetUserPermissions.

Special review required by @manu0466 since he was the one to report the bug (and suggest a solution).

Closes: #800

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[codecov]

Codecov Report

Merging #801 (7c69120) into master (28b4a2e) will increase coverage by 0.06%.
The diff coverage is 87.32%.

@@            Coverage Diff             @@
##           master     #801      +/-   ##
==========================================
+ Coverage   81.28%   81.35%   +0.06%     
==========================================
  Files          77       78       +1     
  Lines        6610     6681      +71     
==========================================
+ Hits         5373     5435      +62     
- Misses        989      995       +6     
- Partials      248      251       +3     

Impacted Files	Coverage Δ
x/subspaces/legacy/v2/store.go	84.21% <84.21%> (ø)
x/subspaces/keeper/msg_server.go	85.41% <100.00%> (+0.23%)	⬆️
x/subspaces/types/permissions.go	73.52% <100.00%> (+8.14%)	⬆️

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[manu0466]

Looks good to me 👍

[leobragaz]

👍