refactor: isolate mutability and emit missing events

[cgorenflo]

No description provided.

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (ece3349) 89.56% compared to head (f51b390) 89.51%.

Files	Patch %	Lines
contracts/gateway/src/state.rs	97.40%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #260      +/-   ##
==========================================
- Coverage   89.56%   89.51%   -0.05%     
==========================================
  Files         161      162       +1     
  Lines       17050    16902     -148     
==========================================
- Hits        15270    15129     -141     
+ Misses       1780     1773       -7     

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