feat(server): support cancellation of running generation jobs (#2190)

examples/server/routes_sdcpp.cpp

@@ -206,7 +206,7 @@ static json make_img_gen_features_json() {
         {"hires", true},
         {"cache", true},
         {"cancel_queued", true},
-        {"cancel_generating", false},
+        {"cancel_generating", true},
         {"preview", true},
     };
 }
@@ -221,7 +221,7 @@ static json make_vid_gen_features_json() {
         {"vae_tiling", true},
         {"cache", true},
         {"cancel_queued", true},
-        {"cancel_generating", false},
+        {"cancel_generating", true},
         {"preview", true},
     };
 }
@@ -380,8 +380,8 @@ static json make_capabilities_json(ServerRuntime& runtime) {
     json top_level_defaults       = json::object();
     json top_level_output_formats = json::array();
     json top_level_features       = {
-              {"cancel_queued", true},
-              {"cancel_generating", false},
+        {"cancel_queued", true},
+        {"cancel_generating", true},
     };
     std::string current_mode = "";
     if (supports_img) {
@@ -840,8 +840,9 @@ void register_sdcpp_api_endpoints(httplib::Server& svr, ServerRuntime& rt) {
         }
 
         if (job.status == AsyncJobStatus::Generating) {
-            res.status = 409;
-            res.set_content(R"({"error":"job is currently generating and cannot be interrupted yet"})", "application/json");
+            job.cancel_requested.store(true);
+            res.status = 200;
+            res.set_content(make_async_job_json(manager, job).dump(), "application/json");
             return;
         }