fix: add missing email reply validation (#1934)

## Description

General fixes to the email domain features

Changes made:
- Add "email" validation for "Reply-To email" fields
- Fix issue where you can't remove the "Reply-To" email after it's set
- Fix issue where setting the "Sender email" back to Documenso would
still send using the org/team pref

packages/ui/primitives/document-flow/add-subject.types.ts

@@ -6,7 +6,10 @@ import { ZDocumentEmailSettingsSchema } from '@documenso/lib/types/document-emai
 export const ZAddSubjectFormSchema = z.object({
   meta: z.object({
     emailId: z.string().nullable(),
-    emailReplyTo: z.string().email().optional(),
+    emailReplyTo: z.preprocess(
+      (val) => (val === '' ? undefined : val),
+      z.string().email().optional(),
+    ),
     // emailReplyName: z.string().optional(),
     subject: z.string(),
     message: z.string(),

packages/ui/primitives/template-flow/add-template-settings.types.tsx

@@ -49,7 +49,10 @@ export const ZAddTemplateSettingsFormSchema = z.object({
       .optional()
       .default('en'),
     emailId: z.string().nullable(),
-    emailReplyTo: z.string().optional(),
+    emailReplyTo: z.preprocess(
+      (val) => (val === '' ? undefined : val),
+      z.string().email().optional(),
+    ),
     emailSettings: ZDocumentEmailSettingsSchema,
     signatureTypes: z.array(z.nativeEnum(DocumentSignatureType)).min(1, {
       message: msg`At least one signature type must be enabled`.id,