DOC: Update documentation about CacheMixin

Author: kamil-certat

CHANGELOG.md

@@ -13,6 +13,8 @@
 
 ### Core
 - `intelmq.lib.utils.drop_privileges`: When IntelMQ is called as `root` and dropping the privileges to user `intelmq`, also set the non-primary groups associated with the `intelmq` user. Makes the behaviour of running intelmqctl as `root` closer to the behaviour of `sudo -u intelmq ...` (PR#2507 by Mikk Margus Möll).
+- `intelmq.lib.mixins.cache.CacheMixin` was extended to support temporary storing messages in a cache queue
+  (PR#2509 by Kamil Mankowski).
 
 ### Development
 

docs/dev/bot-development.md

@@ -197,14 +197,26 @@ The `CacheMixin` provides methods to cache values for bots in a Redis database.
 - `redis_cache_ttl: int = 15`
 - `redis_cache_password: Optional[str] = None`
 
-and provides the methods:
+and provides the methods to cache key-value pairs:
 
 - `cache_exists`
 - `cache_get`
 - `cache_set`
 - `cache_flush`
 - `cache_get_redis_instance`
 
+and following methods to cache objects in a queue:
+
+- `cache_put`
+- `cache_pop`
+- `cache_length`.
+
+Caching key-value pairs and queue caching are two separated mechanisms. The first is designed
+ for arbitrary values, the second one is focused on temporary storing messages (but can handle other
+ data). You won't see caches from one in the another. For example, if adding a key-value pair using
+ `cache_set`, it does not change the value from `cache_length`, and if adding an element using
+ `cache_put` you cannot use `check_exists` to look for it.
+
 ### Pipeline Interactions
 
 We can call three methods related to the pipeline:

intelmq/lib/mixins/cache.py

@@ -13,7 +13,7 @@
 
 
 class CacheMixin:
-    """Provides caching possibilities for bots
+    """Provides caching possibilities for bots, see also https://docs.intelmq.org/latest/dev/bot-development/#mixins
 
     For key-value cache, use methods:
         cache_exists