Add `toSchema` function, to convert any legacy normalizer into a zod schema

app/soapbox/utils/normalizers.ts

@@ -1,3 +1,5 @@
+import z from 'zod';
+
 /** Use new value only if old value is undefined */
 export const mergeDefined = (oldVal: any, newVal: any) => oldVal === undefined ? newVal : oldVal;
 
@@ -10,3 +12,18 @@ export const makeEmojiMap = (emojis: any) => emojis.reduce((obj: any, emoji: any
 export const normalizeId = (id: any): string | null => {
   return typeof id === 'string' ? id : null;
 };
+
+export type Normalizer<V, R> = (value: V) => R;
+
+/**
+ * Allows using any legacy normalizer function as a zod schema.
+ *
+ * @example
+ * ```ts
+ * const statusSchema = toSchema(normalizeStatus);
+ * statusSchema.parse(status);
+ * ```
+ */
+export const toSchema = <V, R>(normalizer: Normalizer<V, R>) => {
+  return z.custom<V>().transform<R>(normalizer);
+};