FEATURE: Default Composer Category Site Setting (#18967)

* FEATURE: Default Composer Category Site Setting

- Create the default_composer_category site setting
- Replace general_category_id logic for auto selecting the composer
  category
- Prevent Uncategorized from being selected if not allowed
- Add default_composer_category option to seeded categories
- Create a migration to populate the default_composer_category site
  setting if there is a general_category_id populated
- Added some tests

* Add missing translation for the new site setting

* fix some js tests

* Just check that the header value is null

db/migrate/20221110175456_populate_default_composer_category.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+## If the general_category_id has a value, set the *new*
+# default_composer_category site setting to match
+
+class PopulateDefaultComposerCategory < ActiveRecord::Migration[7.0]
+  def up
+    general_category_id = DB.query_single("SELECT value FROM site_settings WHERE name = 'general_category_id'")
+    return if general_category_id.blank? || general_category_id[0].to_i < 0
+    default_composer_category = DB.query_single("SELECT value FROM site_settings where name = 'default_composer_category'")
+    return if !default_composer_category.blank?
+    DB.exec(
+      "INSERT INTO site_settings(name, value, data_type, created_at, updated_at)
+      VALUES('default_composer_category', :setting, '16', NOW(), NOW())",
+      setting: general_category_id[0].to_i
+    )
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end