docs: add note to encourage implementation of _validate and _finalize

docs/source/finam-book/development/components.rst

@@ -189,6 +189,10 @@ This is done in :meth:`.TimeComponent._connect`.
 
 After this connection phase, models can validate their state in :meth:`.TimeComponent._validate`. We do nothing there.
 
+.. note::
+
+    It is not strictly required to implement `_validate` but it is highly encouraged to do so.
+
 .. code-block:: Python
 
     # imports...
@@ -315,6 +319,10 @@ In method :meth:`.TimeComponent._finalize`, the component can do any cleanup req
 
 We do nothing special here.
 
+.. note::
+
+    It is not strictly required to implement `_finalize` but it is highly encouraged to do so.
+
 .. code-block:: Python
 
     # imports...