Apply some clippy lint where it makes sense

[ptondereau]

No big deals here, and just applying some clippy rules that make sense.
Please don't hesitate to close if it's not relevant

[codspeed-hq]

CodSpeed Performance Report

Merging #226 will not alter performance

_{Comparing ptondereau:clippy-hunt (9043f42) with main (71f4350)}

Summary

✅ 12 untouched benchmarks

[codecov]

Codecov Report

Attention: Patch coverage is 51.51515% with 16 lines in your changes missing coverage. Please review.

Project coverage is 67.51%. Comparing base (71f4350) to head (9043f42).

Files	Patch %	Lines
biscuit-auth/src/token/builder.rs	16.66%	5 Missing ⚠️
biscuit-quote/src/lib.rs	0.00%	4 Missing ⚠️
biscuit-auth/src/token/authorizer.rs	66.66%	3 Missing ⚠️
biscuit-auth/src/datalog/mod.rs	83.33%	1 Missing ⚠️
biscuit-auth/src/datalog/symbol.rs	50.00%	1 Missing ⚠️
biscuit-auth/src/format/convert.rs	0.00%	1 Missing ⚠️
biscuit-auth/src/token/authorizer/snapshot.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #226      +/-   ##
==========================================
+ Coverage   67.47%   67.51%   +0.03%     
==========================================
  Files          25       25              
  Lines        5347     5347              
==========================================
+ Hits         3608     3610       +2     
+ Misses       1739     1737       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[Geal]

thanks!