Consolidate template object building and context application

Replaces `build_template_object` and `apply_import_context` with a single
`prepare_import_model` orchestrator that handles the whole pipeline:
build the template object → assign form params (if any) → apply context.

Both `:import` and `:do_import` collection actions now call one method
instead of two, and the form-params extraction is encapsulated inside the
helper instead of being duplicated at the call site.

Author: Fivell

lib/active_admin_import/dsl.rb

@@ -27,16 +27,18 @@ module ActiveAdminImport
   module DSL
     CONTEXT_METHOD = :active_admin_import_context
 
-    def self.build_template_object(template_object)
-      template_object.is_a?(Proc) ? template_object.call : template_object
-    end
-
-    def self.apply_import_context(model, controller)
-      return unless controller.respond_to?(CONTEXT_METHOD, true)
+    def self.prepare_import_model(template_object, controller, params: nil)
+      model = template_object.is_a?(Proc) ? template_object.call : template_object
+      if params
+        params_key = ActiveModel::Naming.param_key(model.class)
+        model.assign_attributes(params[params_key].try(:deep_symbolize_keys) || {})
+      end
+      return model unless controller.respond_to?(CONTEXT_METHOD, true)
       context = controller.send(CONTEXT_METHOD)
-      return unless context.is_a?(Hash)
+      return model unless context.is_a?(Hash)
       context = context.merge(file: model.file) if model.respond_to?(:file) && !context.key?(:file)
       model.assign_attributes(context)
+      model
     end
 
     DEFAULT_RESULT_PROC = lambda do |result, options|
@@ -71,8 +73,7 @@ def active_admin_import(options = {}, &block)
 
       collection_action :import, method: :get do
         authorize!(ActiveAdminImport::Auth::IMPORT, active_admin_config.resource_class)
-        @active_admin_import_model = ActiveAdminImport::DSL.build_template_object(options[:template_object])
-        ActiveAdminImport::DSL.apply_import_context(@active_admin_import_model, self)
+        @active_admin_import_model = ActiveAdminImport::DSL.prepare_import_model(options[:template_object], self)
         render template: options[:template]
       end
 
@@ -89,10 +90,9 @@ def active_admin_import(options = {}, &block)
         authorize!(ActiveAdminImport::Auth::IMPORT, active_admin_config.resource_class)
         _params = params.respond_to?(:to_unsafe_h) ? params.to_unsafe_h : params
         params = ActiveSupport::HashWithIndifferentAccess.new _params
-        @active_admin_import_model = ActiveAdminImport::DSL.build_template_object(options[:template_object])
-        params_key = ActiveModel::Naming.param_key(@active_admin_import_model.class)
-        @active_admin_import_model.assign_attributes(params[params_key].try(:deep_symbolize_keys) || {})
-        ActiveAdminImport::DSL.apply_import_context(@active_admin_import_model, self)
+        @active_admin_import_model = ActiveAdminImport::DSL.prepare_import_model(
+          options[:template_object], self, params: params
+        )
         # go back to form
         return render template: options[:template] unless @active_admin_import_model.valid?
         @importer = Importer.new(