Add default value for file_store to PipelineArtifact

By adding a default value we no longer need to specify
the file_store during object creation. This is similar
to our current JobArtifact model.

changelogs/unreleased/mo-add-default-value-to-pipeline-artifact.yml

+---
+title: Add default value for file_store to ci_pipeline_artifacts
+merge_request: 39349
+author:
+type: fixed

db/migrate/20200811194848_add_default_value_for_file_store_to_pipeline_artifact.rb

+# frozen_string_literal: true
+
+class AddDefaultValueForFileStoreToPipelineArtifact < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  PIPELINE_ARTIFACT_LOCAL_FILE_STORE = 1
+
+  def up
+    with_lock_retries do
+      change_column_default :ci_pipeline_artifacts, :file_store, PIPELINE_ARTIFACT_LOCAL_FILE_STORE
+    end
+  end
+
+  def down
+    with_lock_retries do
+      change_column_default :ci_pipeline_artifacts, :file_store, nil
+    end
+  end
+end

db/schema_migrations/20200811194848

+c45bbd5aa9143e039d41448f1cb4a2e8e0a7b2c165b50e89b1b829bbbe81f137
\ No newline at end of file

db/structure.sql

@@ -10061,7 +10061,7 @@ CREATE TABLE public.ci_pipeline_artifacts (
     pipeline_id bigint NOT NULL,
     project_id bigint NOT NULL,
     size integer NOT NULL,
-    file_store smallint NOT NULL,
+    file_store smallint DEFAULT 1 NOT NULL,
     file_type smallint NOT NULL,
     file_format smallint NOT NULL,
     file text,