[core] Try to fix swagger for redoc

src/structures/files.dto.ts

@@ -15,7 +15,7 @@ export class RemoteFile {
     description: 'Document file name. Value can be null',
     example: 'filename.jpg',
   })
-  filename?: string | null;
+  filename?: string;
 
   @ApiProperty({
     example:
@@ -35,7 +35,7 @@ export class BinaryFile {
     description: 'Document file name. Optional',
     example: 'filename.jpeg',
   })
-  filename?: string | null;
+  filename?: string;
 
   @ApiProperty({
     description: 'Base64-encoded data of the file',

src/structures/responses.dto.ts

@@ -4,7 +4,7 @@ import { WAMessageAck } from './enums.dto';
 import { ChatIdProperty, MessageIdProperty } from './properties.dto';
 
 export class WALocation {
-  description?: string | null;
+  description?: string;
   latitude: string;
   longitude: string;
 }

src/structures/sessions.dto.ts

@@ -78,5 +78,5 @@ export class MeInfo {
 }
 
 export class SessionInfo extends SessionDTO {
-  me: MeInfo | null;
+  me?: MeInfo;
 }