More golangci-lint checks

[julienduchesne]

Activate a bunch more linters following #761
This is mostly style checks like removing snake case variables and not starting error messages with an uppercase. This leads to a more consistent codebase

[github-actions]

Benchstat (compared to main):

name              old time/op    new time/op    delta
GetSnippetHash-2    21.6ms ± 4%    22.4ms ± 5%  +3.66%  (p=0.011 n=10+10)

name              old alloc/op   new alloc/op   delta
GetSnippetHash-2    3.85MB ± 0%    3.86MB ± 0%  +0.08%  (p=0.004 n=9+10)

name              old allocs/op  new allocs/op  delta
GetSnippetHash-2     32.3k ± 0%     32.3k ± 0%  +0.02%  (p=0.013 n=8+10)