[nominatim-web] Add proper healthcheck

[Bartłomiej Piotrowski <bpiotrowski src gnome org>]

commit 84fcee5daa7e17decf4048aef923a55513ed21c3
Author: Bartłomiej Piotrowski <bpiotrowski gnome org>
Date:   Fri Jul 2 13:22:40 2021 +0200

    Add proper healthcheck

 app/main.py | 10 ++++++++++
 1 file changed, 10 insertions(+)
---
diff --git a/app/main.py b/app/main.py
index 0601f70..0d0a330 100644
--- a/app/main.py
+++ b/app/main.py
@@ -43,6 +43,16 @@ def initialize():
 
 @app.get("/status")
 def healthcheck():
+    with postgres.cursor() as cur:
+        cur.execute("SELECT 1")
+        cur.fetchone()
+
+    with postgres_ro.cursor() as cur:
+        cur.execute("SELECT 1")
+        cur.fetchone()
+
+    redis_conn.ping()
+
     return {"status": "OK"}