Road to replacing slice operations with standard lib functions

[muety]

As we're trying to use as few external dependencies as possible in Wakapi, I looked into how duke-git/lancet/slice might be replaced with latest standard library methods.

The following table lists all slice methods we're currently using in the code base. However, looks like there's not yet an stdlib equivalent for all of them (happy to learn otherwise).

Of course, things like Filter could also be written out as a loop, however, I prefer code compactness and readability in this case.

lancet method	stdlib method	lo method
slice.Contain	slices.Contains	tbd
slice.ContainBy	slices.ContainsFunc	tbd
slice.Find	slices.IndexFunc (not quite the same)	tbd
slice.Filter	-	tbd
slice.Unique	slices.Sorted + slices.Compact	tbd
slice.Map	-	tbd
slice.SortByField	slices.SortedFunc	tbd
slice.GroupWith	- (feature request)	tbd

[muety]

Introducing slog-sentry unfortunately brought in lo as another dependency. It does pretty much exactly the same as lancet (I went for lancet, because lo didn't exist at the time (shortly after Go generics were introduced)).

To eliminate lancet as a dependency, I'd propose to:

1. Replace all function calls with stdlib equivalents wherever possible
2. Replace all remaining ones with lo euqivalents
3. Hopefully none are left

Need to fill another column for lo in the table above.

Whoever wants to jump onto this refactoring, go for it! It's super low-prio, though, because there won't be an actual benefit for the user. Only advantage will be one less dependency and thus adds a bit to keeping Wakapi light-weight.