changes

* move error-related code for groups to its own file

* update group avatar logic

remove unused/duplicate logic

* update `FindGroupsOptions.ToConds()`

allow passing `-1` as the `ParentGroupID`, meaning "find matching groups regardless of the parent group id"

* add `DedupeBy` function to container module

this removes duplicate items from a slice using a custom function

* add `SliceMap` util

works like javascripts's `Array.prototoype.map`, taking in a slice and transforming each element with the provided function

* add group service

functions included so far:
- avatar uploading/deletion
- group deletion
- group creation
- group moving (including moving item inside a group)
- group update
- team management
  - add team
  - remove team
  - update team permissions
  - recalculating team access (in event of group move)
- group searching (only used in frontend/web components for now)

modules/container/filter.go

@@ -19,3 +19,16 @@ func FilterSlice[E any, T comparable](s []E, include func(E) (T, bool)) []T {
 	}
 	return slices.Clip(filtered)
 }
+
+func DedupeBy[E any, I comparable](s []E, id func(E) I) []E {
+	filtered := make([]E, 0, len(s)) // slice will be clipped before returning
+	seen := make(map[I]bool, len(s))
+	for i := range s {
+		itemId := id(s[i])
+		if _, ok := seen[itemId]; !ok {
+			filtered = append(filtered, s[i])
+			seen[itemId] = true
+		}
+	}
+	return slices.Clip(filtered)
+}