FEATURE: Make General the default category (#18383)

* FEATURE: Make General the default category

* Set general as the default category in the composer model instead

* use semicolon

* Enable allow_uncategorized_topics in create_post spec helper for now

* Check if general_category_id is set

* Enable allow_uncategorized_topics for test env

* Provide an option to the create_post helper to not set allow_uncategorized_topics

* Add tests to check that category… is not present and that General is selected automatically

db/migrate/20220927171707_disable_allow_uncategorized_new_sites.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class DisableAllowUncategorizedNewSites < ActiveRecord::Migration[7.0]
+  def up
+    result = execute <<~SQL
+      SELECT created_at
+      FROM schema_migration_details
+      ORDER BY created_at
+      LIMIT 1
+    SQL
+
+    # keep allow uncategorized for existing sites
+    if result.first['created_at'].to_datetime < 1.hour.ago
+      execute <<~SQL
+        INSERT INTO site_settings(name, data_type, value, created_at, updated_at)
+        VALUES('allow_uncategorized_topics', 5, 't', NOW(), NOW())
+        ON CONFLICT (name) DO NOTHING
+      SQL
+    end
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end