Assume tokens with expiry have always expired (#4644)

app/server/appsmith-interfaces/src/main/java/com/appsmith/external/models/OAuth2.java

@@ -86,6 +86,11 @@ public class OAuth2 extends AuthenticationDTO {
                     "Expected datasource to have valid authentication tokens at this point"));
         }
 
+        if (this.authenticationResponse.expiresAt == null) {
+            // If the token did not return with an expiry time, assume that it has always expired
+            return Mono.just(Boolean.TRUE);
+        }
+
         return Mono.just(authenticationResponse.expiresAt.isBefore(Instant.now().plusSeconds(60)));
     }
 }