Validate text limit on designs.filename

This adds a validation to the text limit constraint that was added in
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/33565.

Our database migration guidelines
https://docs.gitlab.com/ee/development/database/strings_and_the_text_data_type.html#add-a-text-limit-constraint-to-an-existing-column
recommend that we only validate the constraint one release after the
constraint was added.

https://gitlab.com/gitlab-org/gitlab/-/issues/220420

changelogs/unreleased/220420-migration-validate-designs-filename-text-limit.yml

+---
+title: Add migration to validate design_management_designs.filename text limit constraint
+merge_request: 43952
+author:
+type: other

db/post_migrate/20201001022100_validate_designs_filename_text_limit.rb

+# frozen_string_literal: true
+
+class ValidateDesignsFilenameTextLimit < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    validate_text_limit :design_management_designs, :filename
+  end
+
+  def down
+    # no-op
+  end
+end

db/schema_migrations/20201001022100

+a581071767c5484e8286951854b0effe04d4b8951f208f10ceb4812940363959
\ No newline at end of file

db/structure.sql

@@ -11412,7 +11412,8 @@ CREATE TABLE design_management_designs (
     project_id integer NOT NULL,
     issue_id integer,
     filename character varying NOT NULL,
-    relative_position integer
+    relative_position integer,
+    CONSTRAINT check_07155e2715 CHECK ((char_length((filename)::text) <= 255))
 );
 
 CREATE SEQUENCE design_management_designs_id_seq
@@ -18147,9 +18148,6 @@ ALTER TABLE ONLY chat_names
 ALTER TABLE ONLY chat_teams
     ADD CONSTRAINT chat_teams_pkey PRIMARY KEY (id);
 
-ALTER TABLE design_management_designs
-    ADD CONSTRAINT check_07155e2715 CHECK ((char_length((filename)::text) <= 255)) NOT VALID;
-
 ALTER TABLE vulnerability_scanners
     ADD CONSTRAINT check_37608c9db5 CHECK ((char_length(vendor) <= 255)) NOT VALID;