Add config.default_form_controllers option for default form Stimulus controllers

app/helpers/trestle/form_helper.rb

@@ -1,16 +1,15 @@
 module Trestle
   module FormHelper
-    DEFAULT_FORM_CONTROLLERS = %w(keyboard-submit form-loading form-error)
-
     # Generates a form for a resource using Rails' #form_for helper.
     #
     # In addition to delegating to #form_for, this helper method:
     #
     # 1) Sets the default form builder to `Trestle::Form::Builder`.
     # 2) Sets the default :as option to match the parameter name
     #    expected by the admin.
-    # 3) Sets default Stimulus controllers on the <form> element:
-    #    "keyboard-submit form-loading form-error"
+    # 3) Sets default Stimulus controllers on the <form> element
+    #    from `Trestle.config.default_form_controllers`.
+    #    (defaults to: "keyboard-submit form-loading form-error")
     # 4) Sets a null/identity ActionView::Base.field_error_proc as
     #    errors are handled by Trestle::Form::Fields::FormGroup.
     # 5) Exposes the yielded form builder instance via the `form` helper.
@@ -26,7 +25,7 @@ def trestle_form_for(instance, **options, &block)
       options[:as] ||= admin.parameter_name
 
       options[:data] ||= {}
-      options[:data][:controller] = (DEFAULT_FORM_CONTROLLERS + Array(options[:data][:controller])).join(" ")
+      options[:data][:controller] = (Trestle.config.default_form_controllers + Array(options[:data][:controller])).join(" ")
 
       form_for(instance, **options) do |f|
         with_identity_field_error_proc do

lib/trestle/configuration.rb

@@ -91,6 +91,9 @@ def helper(*helpers, &block)
     # Default adapter class used by all admin resources
     option :default_adapter, Adapters.compose(Adapters::ActiveRecordAdapter, Adapters::DraperAdapter)
 
+    # List of Stimulus controllers to add to forms by default
+    option :default_form_controllers, %w(keyboard-submit form-loading form-error)
+
     # Register a custom form field class
     def form_field(name, field)
       Form::Builder.register(name, field)

spec/trestle/configuration_spec.rb

@@ -66,6 +66,10 @@
     expect(config.default_adapter.ancestors).to include(Trestle::Adapters::ActiveRecordAdapter, Trestle::Adapters::DraperAdapter)
   end
 
+  it "has a default form controllers configuration option" do
+    expect(config).to have_accessor(:default_form_controllers).with_default(["keyboard-submit", "form-loading", "form-error"])
+  end
+
   it "has a root breadcrumbs configuration option" do
     expect(config).to have_accessor(:root_breadcrumbs).with_default([Trestle::Breadcrumb.new("Home", "/admin")])
   end