Add customizable user roles (#18641)

* Add customizable user roles

* Various fixes and improvements

* Add migration for old settings and fix tootctl role management

app/controllers/admin/users/roles_controller.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+module Admin
+  class Users::RolesController < BaseController
+    before_action :set_user
+
+    def show
+      authorize @user, :change_role?
+    end
+
+    def update
+      authorize @user, :change_role?
+
+      @user.current_account = current_account
+
+      if @user.update(resource_params)
+        redirect_to admin_account_path(@user.account_id), notice: I18n.t('admin.accounts.change_role.changed_msg')
+      else
+        render :show
+      end
+    end
+
+    private
+
+    def set_user
+      @user = User.find(params[:user_id])
+    end
+
+    def resource_params
+      params.require(:user).permit(:role_id)
+    end
+  end
+end