Add admin interface to manage instances subscriptions

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

priv/repo/migrations/20191206144028_create_shares.exs

@@ -0,0 +1,23 @@
+defmodule Mobilizon.Repo.Migrations.CreateShares do
+  use Ecto.Migration
+
+  def up do
+    create table(:shares) do
+      add(:uri, :string, null: false)
+      add(:actor_id, references(:actors, on_delete: :delete_all), null: false)
+      add(:owner_actor_id, references(:actors, on_delete: :delete_all), null: false)
+
+      timestamps()
+    end
+
+    create_if_not_exists(
+      index(:shares, [:uri, :actor_id], unique: true, name: :shares_uri_actor_id_index)
+    )
+  end
+
+  def down do
+    drop_if_exists(index(:shares, [:uri, :actor_id]))
+
+    drop_if_exists(table(:shares))
+  end
+end