Implement config for actors

* Add actor config to the leapp.conf config file
* Add an attribute for configuration schema to LEAPP Actors
* Create API to load config for actors and validate it against the schemas stored in actors.
* Create a function to retrieve the configuration that an actor has specified.

etc/leapp/leapp.conf

@@ -4,3 +4,5 @@ repo_path=/etc/leapp/repos.d/
 [database]
 path=/var/lib/leapp/leapp.db
 
+[actor_config]
+path=/etc/leapp/actor_conf.d/

leapp/actors/__init__.py

@@ -2,6 +2,7 @@
 import os
 import sys
 
+from leapp.actors.config import retrieve_config
 from leapp.compat import string_types
 from leapp.dialogs import Dialog
 from leapp.exceptions import (MissingActorAttributeError, RequestStopAfterPhase, StopActorExecution,
@@ -41,6 +42,11 @@ class Actor(object):
        Write the actor's description as a docstring.
     """
 
+    config_schemas = ()
+    """
+    Defines the structure of the configuration that the actor uses.
+    """
+
     consumes = ()
     """
     Tuple of :py:class:`leapp.models.Model` derived classes defined in the :ref:`repositories <terminology:repository>`
@@ -86,6 +92,7 @@ def serialize(self):
             'path': os.path.dirname(sys.modules[type(self).__module__].__file__),
             'class_name': type(self).__name__,
             'description': self.description or type(self).__doc__,
+            'config_schemas': self.config_schemas,
             'consumes': [c.__name__ for c in self.consumes],
             'produces': [p.__name__ for p in self.produces],
             'tags': [t.__name__ for t in self.tags],
@@ -100,15 +107,20 @@ def __init__(self, messaging=None, logger=None, config_model=None, skip_dialogs=
         This depends on the definition of such a configuration model being defined by the workflow
         and an actor that provides such a message.
         """
+
         Actor.current_instance = self
         install_translation_for_actor(type(self))
         self._messaging = messaging
         self.log = (logger or logging.getLogger('leapp.actors')).getChild(self.name)
         self.skip_dialogs = skip_dialogs
         """ A configured logger instance for the current actor. """
 
+        # self._configuration is the workflow configuration.
+        # self.config_schemas is the actor defined configuration.
+        # self.config is the actual actor configuration
         if config_model:
             self._configuration = next(self.consume(config_model), None)
+        self.config = retrieve_config(self.config_schemas)
 
         self._path = path
 
@@ -470,6 +482,8 @@ def get_actor_metadata(actor):
         _get_attribute(actor, 'dialogs', _is_dialog_tuple, required=False, default_value=()),
         _get_attribute(actor, 'description', _is_type(string_types), required=False,
                        default_value=actor.__doc__ or 'There has been no description provided for this actor.'),
+        _get_attribute(actor, 'config_schemas', _is_type(string_types), required=False,
+                       default_value=actor.__doc__ or 'Description of the configuration used by this actor.')
         _get_attribute(actor, 'apis', _is_api_tuple, required=False, default_value=())
     ])