Textgen: Add model downloading for TabbyAPI

Tabby has a HuggingFace downloader API endpoint. Add direct support
in SillyTavern by using the same method as ollama, but with the correct
parameters exposed.

Signed-off-by: kingbri <bdashore3@proton.me>

src/endpoints/backends/text-completions.js

@@ -588,7 +588,36 @@ llamacpp.post('/slots', jsonParser, async function (request, response) {
     }
 });
 
+const tabby = express.Router();
+
+tabby.post('/download', jsonParser, async function (request, response) {
+    try {
+        const baseUrl = String(request.body.api_server).replace(/\/$/, '');
+
+        const args = {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify(request.body),
+            timeout: 0,
+        }
+
+        setAdditionalHeaders(request, args, baseUrl);
+        const fetchResponse = await fetch(`${baseUrl}/v1/download`, args);
+
+        if (!fetchResponse.ok) {
+            console.log('Download error:', fetchResponse.status, fetchResponse.statusText);
+            return response.status(fetchResponse.status).send({ error: true });
+        }
+
+        return response.send({ ok: true });
+    } catch (error) {
+        console.error(error);
+        return response.status(500);
+    }
+});
+
 router.use('/ollama', ollama);
 router.use('/llamacpp', llamacpp);
+router.use('/tabby', tabby);
 
 module.exports = { router };