[#1335] User: refactored :blocks field into :blocked_users relation.

Introduced UserBlock.

priv/repo/migrations/20191108161911_create_user_blocks.exs

@@ -0,0 +1,14 @@
+defmodule Pleroma.Repo.Migrations.CreateUserBlocks do
+  use Ecto.Migration
+
+  def change do
+    create_if_not_exists table(:user_blocks) do
+      add(:blocker_id, references(:users, type: :uuid, on_delete: :delete_all))
+      add(:blockee_id, references(:users, type: :uuid, on_delete: :delete_all))
+
+      timestamps(updated_at: false)
+    end
+
+    create_if_not_exists(unique_index(:user_blocks, [:blocker_id, :blockee_id]))
+  end
+end

priv/repo/migrations/20191108173911_data_migration_populate_user_blocks.exs

@@ -0,0 +1,50 @@
+defmodule Pleroma.Repo.Migrations.DataMigrationPopulateUserBlocks do
+  use Ecto.Migration
+
+  alias Ecto.Adapters.SQL
+  alias Pleroma.Repo
+
+  require Logger
+
+  def up do
+    {:ok, %{rows: block_rows}} =
+      SQL.query(Repo, "SELECT id, blocks FROM users WHERE blocks != '{}'")
+
+    blockee_ap_ids =
+      Enum.flat_map(
+        block_rows,
+        fn [_, ap_ids] -> ap_ids end
+      )
+      |> Enum.uniq()
+
+    # Selecting ids of all blockees at once in order to reduce the number of SELECT queries
+    {:ok, %{rows: blockee_ap_id_id}} =
+      SQL.query(Repo, "SELECT ap_id, id FROM users WHERE ap_id = ANY($1)", [blockee_ap_ids])
+
+    blockee_id_by_ap_id = Enum.into(blockee_ap_id_id, %{}, fn [k, v] -> {k, v} end)
+
+    Enum.each(
+      block_rows,
+      fn [blocker_id, blockee_ap_ids] ->
+        blocker_uuid = Ecto.UUID.cast!(blocker_id)
+
+        for blockee_ap_id <- blockee_ap_ids do
+          blockee_id = blockee_id_by_ap_id[blockee_ap_id]
+          blockee_uuid = blockee_id && Ecto.UUID.cast!(blockee_id)
+
+          with {:ok, blockee_uuid} <- Ecto.UUID.cast(blockee_id) do
+            execute(
+              "INSERT INTO user_blocks(blocker_id, blockee_id, inserted_at) " <>
+                "VALUES('#{blocker_uuid}'::uuid, '#{blockee_uuid}'::uuid, now()) " <>
+                "ON CONFLICT (blocker_id, blockee_id) DO NOTHING"
+            )
+          else
+            _ -> Logger.warn("Missing reference: (#{blocker_uuid}, #{blockee_id})")
+          end
+        end
+      end
+    )
+  end
+
+  def down, do: :noop
+end