[FEAT] add a clean_cache() method for the cache obj

gargantext/util/db_cache.py

@@ -46,6 +46,9 @@ class ModelCache(dict):
 class Cache:
 
     def __getattr__(self, key):
+        '''
+        lazy init of new modelcaches: self.Node, self.User...
+        '''
         try:
             model = getattr(models, key)
         except AttributeError:
@@ -54,4 +57,15 @@ class Cache:
         setattr(self, key, modelcache)
         return modelcache
 
+
+    def clean_all(self):
+        '''
+        re-init any existing modelcaches
+        '''
+        for modelname in self.__dict__:
+            old_modelcache = getattr(cache, modelname)
+            new_modelcache = ModelCache(old_modelcache._model)
+            del old_modelcache
+            setattr(cache, modelname, new_modelcache)
+
 cache = Cache()