feat(horizon): Added support for customizing the SESSION_ENGINE

Change-Id: Iabe9d3e2b1888a6d7b92231228d78dabd211dfda
Signed-off-by: Saeed Padari <sam137115@gmail.com>

horizon/releasenotes/notes/horizon-4c5d5e3b58c700a0.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    Added support for customizing the SESSION_ENGINE.
+    This enables deployers to select different Django session storage options,
+    such as database-backed or cache-based sessions, according to their environment needs.
+...

horizon/values.yaml

@@ -226,6 +226,8 @@ conf:
         pwd_validator_help_text: '_("Your password must be at least eight (8) characters in length and must include characters from at least two (2) of these groupings: alpha, numeric, and special characters.")'
         session_cookie_secure: "False"
         session_cookie_httponly: "False"
+        session_engine: 'django.contrib.sessions.backends.cache'
+        cache_backend: 'django.core.cache.backends.memcached.PyMemcacheCache'
         secure_proxy_ssl_header: false
         password_autocomplete: "False"
         disallow_iframe_embed: "False"
@@ -401,7 +403,7 @@ conf:
 
         CACHES = {
             'default': {
-                'BACKEND': 'django.core.cache.backends.memcached.PyMemcacheCache',
+                'BACKEND': '{{ .Values.conf.horizon.local_settings.config.cache_backend }}',
                 'LOCATION': '{{ tuple "oslo_cache" "internal" "memcache" . | include "helm-toolkit.endpoints.host_and_port_endpoint_uri_lookup" }}',
             }
         }
@@ -426,7 +428,7 @@ conf:
                 'PORT': '{{ tuple "oslo_db" "internal" "mysql" . | include "helm-toolkit.endpoints.endpoint_port_lookup" }}'
             }
         }
-        SESSION_ENGINE = 'django.contrib.sessions.backends.cached_db'
+        SESSION_ENGINE = '{{ .Values.conf.horizon.local_settings.config.session_engine }}'
 
         # Send email to the console by default
         EMAIL_BACKEND = 'django.core.mail.backends.console.EmailBackend'