Generate IdP Metadata with keystone-manage.

For proper federation setup, an Identity Provider peer needs to
generate metadata that can later be consumed by a federated Service
Provider. Since metadata content doesn't change very often it's
advised to generate a static file and later read its content on demand
(this is out of the scope of this patch). This patch adds required
functionality for utilizing the federation.idp.MetadataGenerator class
from a keystone-manage command line tool. Generated metadata will
be redirected to the stdout.

Change-Id: Ifed1f4e4ede0276b3aba22aa9e236e5e74e2ed93
Implements: bp keystone-to-keystone-federation

keystone/cli.py

@@ -255,11 +255,26 @@ class MappingPurge(BaseApp):
         mapping_manager.driver.purge_mappings(mapping)
 
 
+class SamlIdentityProviderMetadata(BaseApp):
+    """Generate Identity Provider metadata."""
+
+    name = 'saml_idp_metadata'
+
+    @staticmethod
+    def main():
+        # NOTE(marek-denis): Since federation is currently an extension import
+        # corresponding modules only when they are really going to be used.
+        from keystone.contrib.federation import idp
+        metadata = idp.MetadataGenerator().generate_metadata()
+        print(metadata.to_string())
+
+
 CMDS = [
     DbSync,
     DbVersion,
     MappingPurge,
     PKISetup,
+    SamlIdentityProviderMetadata,
     SSLSetup,
     TokenFlush,
 ]