Increase the string limits for regex fields in push_rules

Contributes to https://gitlab.com/gitlab-org/gitlab/-/issues/423445

**Problem**

We have a discrepancy between GitLab database and `db/structure.sql`.
GitLab database contains 255 character limit for regex fields. But this
limit is missing for self-hosted instances and GDK.

**Solution**

Recently we added a Rails validation to prevent regex longer than 511
characters (https://gitlab.com/gitlab-org/gitlab/-/merge_requests/128153).

We can migrate existing columns to match this limit.

It's a three step migration:

1. Add NOT VALID CHECK to verify length of regex fields
2. Validate regex fields
3. Remove any char limits from regex fields

Changelog: changed
EE: true

db/migrate/20230828153646_extend_push_rules_regex_limits.rb

+# frozen_string_literal: true
+
+class ExtendPushRulesRegexLimits < Gitlab::Database::Migration[2.1]
+  disable_ddl_transaction!
+
+  REGEX_COLUMNS = %i[
+    force_push_regex
+    delete_branch_regex
+    commit_message_regex
+    author_email_regex
+    file_name_regex
+    branch_name_regex
+  ].freeze
+
+  LONG_REGEX_COLUMNS = %i[commit_message_negative_regex]
+
+  def up
+    REGEX_COLUMNS.each do |column_name|
+      add_check_constraint :push_rules, "char_length(#{column_name}) <= 511", "#{column_name}_size_constraint",
+        validate: false
+    end
+
+    LONG_REGEX_COLUMNS.each do |column_name|
+      add_check_constraint :push_rules, "char_length(#{column_name}) <= 2047", "#{column_name}_size_constraint",
+        validate: false
+    end
+  end
+
+  def down
+    REGEX_COLUMNS.each do |column_name|
+      remove_check_constraint :push_rules, "#{column_name}_size_constraint"
+    end
+
+    LONG_REGEX_COLUMNS.each do |column_name|
+      remove_check_constraint :push_rules, "#{column_name}_size_constraint"
+    end
+  end
+end

db/migrate/20230830084959_validate_push_rules_constraints.rb

+# frozen_string_literal: true
+
+class ValidatePushRulesConstraints < Gitlab::Database::Migration[2.1]
+  disable_ddl_transaction!
+
+  REGEX_COLUMNS = %i[
+    force_push_regex
+    delete_branch_regex
+    commit_message_regex
+    commit_message_negative_regex
+    author_email_regex
+    file_name_regex
+    branch_name_regex
+  ].freeze
+
+  def up
+    REGEX_COLUMNS.each do |column_name|
+      validate_check_constraint :push_rules, "#{column_name}_size_constraint"
+    end
+  end
+
+  def down
+    # No op
+  end
+end

db/migrate/20230830085501_remove_push_rules_regex_limits.rb

+# frozen_string_literal: true
+
+class RemovePushRulesRegexLimits < Gitlab::Database::Migration[2.1]
+  def up
+    change_column :push_rules, :force_push_regex, :string, limit: nil
+    change_column :push_rules, :delete_branch_regex, :string, limit: nil
+    change_column :push_rules, :commit_message_regex, :string, limit: nil
+    change_column :push_rules, :commit_message_negative_regex, :string, limit: nil
+    change_column :push_rules, :author_email_regex, :string, limit: nil
+    change_column :push_rules, :file_name_regex, :string, limit: nil
+    change_column :push_rules, :branch_name_regex, :string, limit: nil
+  end
+
+  def down
+    # No op
+  end
+end

db/schema_migrations/20230828153646

+913b2384ea76d9169020253dacf14a51ccb7ebbaee9c9bc62b0e0473734ed981
\ No newline at end of file

db/schema_migrations/20230830084959

+3469c47c0cd4c86c7d1c9da450493a882d3a5f371fb7b78f49af64a837f989fb
\ No newline at end of file

db/schema_migrations/20230830085501

+5756f155e295263ea8376b9161c523f9ee39628be289d1939c220852abd4d098
\ No newline at end of file

db/structure.sql

@@ -22141,7 +22141,14 @@ CREATE TABLE push_rules (
     regexp_uses_re2 boolean DEFAULT true,
     commit_message_negative_regex character varying,
     reject_non_dco_commits boolean,
-    commit_committer_name_check boolean DEFAULT false NOT NULL
+    commit_committer_name_check boolean DEFAULT false NOT NULL,
+    CONSTRAINT author_email_regex_size_constraint CHECK ((char_length((author_email_regex)::text) <= 511)),
+    CONSTRAINT branch_name_regex_size_constraint CHECK ((char_length((branch_name_regex)::text) <= 511)),
+    CONSTRAINT commit_message_negative_regex_size_constraint CHECK ((char_length((commit_message_negative_regex)::text) <= 2047)),
+    CONSTRAINT commit_message_regex_size_constraint CHECK ((char_length((commit_message_regex)::text) <= 511)),
+    CONSTRAINT delete_branch_regex_size_constraint CHECK ((char_length((delete_branch_regex)::text) <= 511)),
+    CONSTRAINT file_name_regex_size_constraint CHECK ((char_length((file_name_regex)::text) <= 511)),
+    CONSTRAINT force_push_regex_size_constraint CHECK ((char_length((force_push_regex)::text) <= 511))
 );
 CREATE SEQUENCE push_rules_id_seq

ee/spec/requests/api/project_push_rule_spec.rb

@@ -216,8 +216,8 @@
           context 'when feature flag "add_validation_for_push_rules" is disabled' do
             let(:add_validation_for_push_rules_ff) { false }
-            it 'is successful' do
-              expect(response).to have_gitlab_http_status(:created)
+            it 'returns a server error' do
+              expect(response).to have_gitlab_http_status(:server_error)
             end
           end
         end