add CACHE_REDIS_HOST as env variable to config.py

This is usefull for hosts not being "redis"

config.py

@@ -22,7 +22,7 @@ class Config:
     DISPLAY_EXTENDED_AUDIO_DATA = os.getenv('DISPLAY_EXTENDED_AUDIO_DATA',"false").lower() == 'true' 
     CACHE_TYPE = 'redis'
     CACHE_REDIS_PORT = 6379
-    CACHE_REDIS_HOST = 'redis'
+    CACHE_REDIS_HOST = os.getenv('CACHE_REDIS_HOST','redis')
     CACHE_REDIS_DB = 0
     CACHE_DEFAULT_TIMEOUT = 3600
     REDIS_URL = os.getenv('REDIS_URL','redis://redis:6379/0')
@@ -80,4 +80,4 @@ class Config:
         if missing_vars:
             missing = ', '.join(missing_vars)
             sys.stderr.write(f"Error: The following environment variables are not set: {missing}\n")
-            sys.exit(1)
+            sys.exit(1)