rename saved attachment to session-... rather than signal-

ts/test/types/Attachment_test.ts

@@ -50,7 +50,7 @@ describe('Attachment', () => {
           attachment,
           timestamp,
         });
-        const expected = 'signal-attachment-2000-01-01-000000.mov';
+        const expected = 'session-attachment-2000-01-01-000000.mov';
         assert.strictEqual(actual, expected);
       });
     });
@@ -66,7 +66,7 @@ describe('Attachment', () => {
           timestamp,
           index: 3,
         });
-        const expected = 'signal-attachment-1970-01-01-000000_003.mov';
+        const expected = 'session-attachment-1970-01-01-000000_003.mov';
         assert.strictEqual(actual, expected);
       });
     });

ts/types/Attachment.ts

@@ -361,7 +361,7 @@ export const getSuggestedFilename = ({
     return attachment.fileName;
   }
 
-  const prefix = 'signal-attachment';
+  const prefix = 'session-attachment';
   const suffix = timestamp
     ? moment(timestamp).format('-YYYY-MM-DD-HHmmss')
     : '';