Add support for Replicate feature

Pulp Container now supports the Replication feature.

closes pulp#1648

CHANGES/1648.feature

@@ -0,0 +1,3 @@
+Added support for the Replication feature. The replication process allows a Pulp instance to
+replicate container repositories from an upstream Pulp, creating the required remotes,
+repositories, and distributions.

pulp_container/app/replica.py

@@ -0,0 +1,53 @@
+from pulpcore.plugin.replica import Replicator
+from pulpcore.plugin.util import get_url
+
+from pulp_glue.container.context import (
+    PulpContainerDistributionContext,
+    PulpContainerRepositoryContext,
+)
+
+from pulp_container.app.models import ContainerDistribution, ContainerRemote, ContainerRepository
+from pulp_container.app.tasks import synchronize as container_synchronize
+
+
+class ContainerReplicator(Replicator):
+    distribution_ctx_cls = PulpContainerDistributionContext
+    repository_ctx_cls = PulpContainerRepositoryContext
+    remote_model_cls = ContainerRemote
+    repository_model_cls = ContainerRepository
+    distribution_model_cls = ContainerDistribution
+    distribution_serializer_name = "ContainerDistributionSerializer"
+    repository_serializer_name = "ContainerRepositorySerializer"
+    remote_serializer_name = "ContainerRemoteSerializer"
+    app_label = "container"
+    sync_task = container_synchronize
+
+    def sync_params(self, repository, remote):
+        """Returns a dictionary where key is a parameter for the sync task."""
+        return dict(
+            remote_pk=str(remote.pk),
+            repository_pk=str(repository.pk),
+            signed_only=False,
+            mirror=True,
+        )
+
+    def url(self, upstream_distribution):
+        return self.pulp_ctx._api_kwargs["base_url"]
+
+    def remote_extra_fields(self, upstream_distribution):
+        upstream_name = upstream_distribution["registry_path"].split("/")[1]
+        return {"upstream_name": upstream_name}
+
+    def distribution_data(self, repository, upstream_distribution):
+        """
+        Return the fields that need to be updated/cleared on distributions for idempotence.
+        """
+        return {
+            "repository": get_url(repository),
+            "base_path": upstream_distribution["base_path"],
+            "private": upstream_distribution["private"],
+            "description": upstream_distribution["description"],
+        }
+
+
+REPLICATION_ORDER = [ContainerReplicator]