Implement editing of slots in ClientSchedule

Implement tracking of time slots along with editing and restoration of
singularly edited time slots.  This provides a simpler interface to work
with when rendering tables of time slots that can be edited than
directly manipulating events and shifts containing an array of slots.

shared/utils/functions.ts

@@ -78,3 +78,26 @@ export function setEquals<T>(...sets: Set<T>[]) {
 	}
 	return true;
 }
+
+/**
+	Returns true if the two maps passed as input compare equal to each other.
+	@param a Input map
+	@param b Input map
+	@param equals Function to compare individual values in the map.
+	@returns True if the maps compare equal
+*/
+export function mapEquals<K, V>(
+	a: Map<K, V>,
+	b: Map<K, V>,
+	equals: (a: V, b: V) => unknown = (a, b) => a === b,
+) {
+	if (a.size !== b.size) {
+		return false;
+	}
+	for (const [key, value] of a) {
+		if (!b.has(key) || value !== b.get(key)) {
+			return false;
+		}
+	}
+	return true;
+}