Merge branch 'refactor/db-not-null-constraints-for-registrations' into 'develop'

Add NOT NULL constraints for registrations table

See merge request pleroma/pleroma!1906

priv/repo/migrations/20191026191635_set_not_null_for_registrations.exs

+defmodule Pleroma.Repo.Migrations.SetNotNullForRegistrations do
+  use Ecto.Migration
+
+  # modify/3 function will require index recreation, so using execute/1 instead
+
+  def up do
+    execute("ALTER TABLE registrations
+    ALTER COLUMN provider SET NOT NULL,
+    ALTER COLUMN uid SET NOT NULL,
+    ALTER COLUMN info SET NOT NULL")
+  end
+
+  def down do
+    execute("ALTER TABLE registrations
+    ALTER COLUMN provider DROP NOT NULL,
+    ALTER COLUMN uid DROP NOT NULL,
+    ALTER COLUMN info DROP NOT NULL")
+  end
+end