only set session (cookie) lang on changes

src/capport/api/lang.py

@@ -1,9 +1,10 @@
 from __future__ import annotations
 
+import os.path
 import re
 import typing
+
 import quart
-import os.path
 
 from .app import app
 
@@ -53,7 +54,8 @@ def detect_language():
     if 'setlang' in r.args:
         lang = r.args.get('setlang').strip().lower()
         if lang and _VALID_LANGUAGE_NAMES.match(lang):
-            s['lang'] = lang
+            if s.get('lang') != lang:
+                s['lang'] = lang
             g.langs = [lang]
             return
         else: