Add command and query for organizations

* Added command and query for organizations
* Saving unknown organizations into database in `background` service
* Added `List` method in `OrganizationRepository`

internal/common/xslices/foreach.go

@@ -5,3 +5,11 @@ func ForEach[T any](items []T, f func(T)) {
 		f(item)
 	}
 }
+
+func AsMap[T any, U comparable](items []T, f func(T) U) map[U]struct{} {
+	out := make(map[U]struct{}, len(items))
+	ForEach(items, func(in T) {
+		out[f(in)] = struct{}{}
+	})
+	return out
+}