configuration: the cache folder can now be specified in the configuration file

chatmastermind/configuration.py

@@ -116,6 +116,7 @@ class Config:
     """
     # all members have default values, so we can easily create
     # a default configuration
+    cache: str = '.'
     db: str = './db/'
     ais: dict[str, AIConfig] = field(default_factory=create_default_ai_configs)
 
@@ -132,6 +133,7 @@ class Config:
             ai_conf = ai_config_instance(conf['name'], conf)
             ais[ID] = ai_conf
         return cls(
+            cache=str(source['cache']) if 'cache' in source else '.',
             db=str(source['db']),
             ais=ais
         )