little changes for MRF config descriptions

- log level reduction, if policy doesn't implement config_description method
- docs in dev.md

docs/dev.md

@@ -21,3 +21,26 @@ This document contains notes and guidelines for Pleroma developers.
 ## Auth-related configuration, OAuth consumer mode etc.
 
 See `Authentication` section of [the configuration cheatsheet](configuration/cheatsheet.md#authentication).
+
+## MRF policies descriptions
+
+If MRF policy depends on config, it can be added into MRF tab to adminFE by adding `config_description/0` method, which returns map with special structure.
+
+Example:
+
+```elixir
+%{
+      key: :mrf_activity_expiration,
+      related_policy: "Pleroma.Web.ActivityPub.MRF.ActivityExpirationPolicy",
+      label: "MRF Activity Expiration Policy",
+      description: "Adds automatic expiration to all local activities",
+      children: [
+        %{
+          key: :days,
+          type: :integer,
+          description: "Default global expiration time for all local activities (in days)",
+          suggestions: [90, 365]
+        }
+      ]
+    }
+```

lib/pleroma/web/activity_pub/mrf.ex

@@ -164,7 +164,7 @@ def config_descriptions(policies) do
           acc
         end
       else
-        Logger.info(
+        Logger.debug(
           "#{policy} is excluded from config descriptions, because does not implement `config_description/0` method."
         )