Generate schemas dynamically from pieces provided by each object class

This way we benefit from:
* knowing which attributes are used/required by each object class and
  subclass
* Having validation function definitions near the class going to use them

Change-Id: I8fd6773c51d19405a585977af4ed72cad2b21db1
diff --git a/src/osmo_gsm_tester/obj/epc.py b/src/osmo_gsm_tester/obj/epc.py
index f6bddea..c725f76 100644
--- a/src/osmo_gsm_tester/obj/epc.py
+++ b/src/osmo_gsm_tester/obj/epc.py
@@ -19,7 +19,14 @@
 
 from abc import ABCMeta, abstractmethod
 from ..core import log, config
+from ..core import schema
 
+def on_register_schemas():
+    config_schema = {
+        'type': schema.STR,
+        'qci': schema.UINT,
+        }
+    schema.register_config_schema('epc', config_schema)
 
 class EPC(log.Origin, metaclass=ABCMeta):