Added a few changes to query expressions (#51)

- Added the between operator to query expressions.
- Added the using query expression suffix to specify which index to query (or force a scan). This is required if query planning has found multiple indices that can potentially be used.
- Rewrote the types of the query expressions to allow for functions to be defined once, and be useful in queries that result in DynamoDB queries, and evaluation.
- Added some test functions around time and summing numbers.
- Fixed a bug in the del-attr which was not honouring marked rows in a similar way to set-attr: it was only deleting attributes from the first row.
- Added the -to type flag to set-attr which will set the attribute to the value of a query expression.

internal/common/maputils/map.go

@@ -8,6 +8,16 @@ func Values[K comparable, T any](ts map[K]T) []T {
 	return values
 }
 
+func MapValues[K comparable, T, U any](ts map[K]T, fn func(t T) U) map[K]U {
+	us := make(map[K]U)
+
+	for k, t := range ts {
+		us[k] = fn(t)
+	}
+
+	return us
+}
+
 func MapValuesWithError[K comparable, T, U any](ts map[K]T, fn func(t T) (U, error)) (map[K]U, error) {
 	us := make(map[K]U)