chore: Clean up report & knowledge base policies (#11234)

- Removes the portal_members table and all associated records
- Updates policies to use custom roles with knowledge_base_manage
permission
- Updates controllers, models, and views to work without portal
membership
- Adds tests for the new permission model

app/controllers/api/v2/accounts/reports_controller.rb

@@ -66,9 +66,7 @@ class Api::V2::Accounts::ReportsController < Api::V1::Accounts::BaseController
   end
 
   def check_authorization
-    return if Current.account_user.administrator?
-
-    raise Pundit::NotAuthorizedError
+    authorize :report, :view?
   end
 
   def common_params
@@ -137,5 +135,3 @@ class Api::V2::Accounts::ReportsController < Api::V1::Accounts::BaseController
     V2::ReportBuilder.new(Current.account, conversation_params).conversation_metrics
   end
 end
-
-Api::V2::Accounts::ReportsController.prepend_mod_with('Api::V2::Accounts::ReportsController')