docs: clarify beforeSave usage and return contract in create hook

Author: NoOne7135

adminforth/types/Back.ts

@@ -1346,9 +1346,13 @@ export interface AdminForthResource extends Omit<AdminForthResourceInput, 'optio
     },
     create?: {
       /**
+       * Should return ok: true to continue saving pipeline and allow creating record in database, and ok: false to interrupt pipeline and prevent record creation.
+       * If you need to show error on UI, set error: <error message> in response.
+       * 
        * Typical use-cases:
-       * - Validate record before saving to database and interrupt execution if validation failed (`allowedActions.create` should be preferred in most cases)
-       * - fill-in adminUser as creator of record
+       * - Create record by custom code (return  `{ ok: false, newRecordId: <id of created record from custom code>}`)
+       * - Validate record before saving to database and interrupt execution if validation failed (return `{ok: false, error: <validation error>}`), though `allowedActions.create` should be preferred in most cases
+       * - fill-in adminUser as creator of record (set record.<some field> = x; return {ok: true})
        * - Attach additional data to record before saving to database (mostly fillOnCreate should be used instead)
        */
       beforeSave?: Array<BeforeCreateSaveFunction>,