fix: support dynamic external ids for direct templates (#1274)

Adds support for an `externalId` query param to be passed when linking a
user to a direct template. This external id will then be stored on the
document upon signing completion.

packages/trpc/server/template-router/schema.ts

@@ -20,6 +20,7 @@ export const ZCreateDocumentFromDirectTemplateMutationSchema = z.object({
   directRecipientName: z.string().optional(),
   directRecipientEmail: z.string().email(),
   directTemplateToken: z.string().min(1),
+  directTemplateExternalId: z.string().optional(),
   signedFieldValues: z.array(ZSignFieldWithTokenMutationSchema),
   templateUpdatedAt: z.date(),
 });