Fix missing prometheus commit (#16415)

* Add prometheus metrics

* add docs for metrics

* sidebar

* lint

* lint

---------

Co-authored-by: Mitch Ross <mitchross@users.noreply.github.com>

frigate/api/app.py

@@ -18,6 +18,7 @@ from fastapi.params import Depends
 from fastapi.responses import JSONResponse, PlainTextResponse
 from markupsafe import escape
 from peewee import operator
+from prometheus_client import CONTENT_TYPE_LATEST, generate_latest
 from pydantic import ValidationError
 
 from frigate.api.defs.query.app_query_parameters import AppTimelineHourlyQueryParameters
@@ -108,6 +109,12 @@ def stats_history(request: Request, keys: str = None):
     return JSONResponse(content=request.app.stats_emitter.get_stats_history(keys))
 
 
+@router.get("/metrics")
+def metrics():
+    """Expose Prometheus metrics endpoint"""
+    return Response(content=generate_latest(), media_type=CONTENT_TYPE_LATEST)
+
+
 @router.get("/config")
 def config(request: Request):
     config_obj: FrigateConfig = request.app.frigate_config