Restrict Content Pro 3.5.41

Modified template files: subscription.php
New: Add filters on admin Payment Received email message and subject. rcp_payment_received_admin_email and rcp_email_payment_received_admin_subject.
New: Add user_id column to memberships table. This helps provide a more direct connection between a membership record and the corresponding user account. This data will be automatically backfilled when accessed.
New: Add get_payment_id() public method to RCP_Emails class.
Improvement: Add JavaScript confirmation to "Cancel" link on admin memberships table.
Improvement: Automatically retry failed payment after Stripe billing card is updated.
Improvement: Add more detail to "can cancel" debug log message to explain why it might be "false".
Improvement: Include all method parameters in rcp_registration_get_recurring_total filter.
Improvement: Rework handling in 3.0 migration for people who attempt the migration multiple times. This helps better ensure all migrated data is brand new and not "stale" from the previous attempt.
Improvement: Adjust membership level "Status" description to clarify the difference between active and inactive membership levels.
Improvement: Introduce rcp_transition_customer_email_verification hook. This hook is now used for triggering email verification emails.
Improvement: Add $payment_event parameter to rcp_stripe_webhook_membership filter.
Improvement: subscription.php template - Give upgrade link a new class (rcp_sub_details_change_membership) so it's not the same as the renew link.
Fix: "Complete Payment" feature not working - form gets stuck on "Please Wait..."
Fix: RCP duplicating Google Authenticator plugin's admin settings.
Fix: Invalid integer error while processing failed payment emails.
Fix: Ensure RCP's new membership expiration date is always at least 2 hours after Stripe's reported current_period_end on automatic renewals. This allows time for Stripe's 1-hour window between invoice generation and payment.
Fix: Rework old discounts database table upgrades from the 3.0.0 update to ensure they all run correctly and in order. This protects against a possible error about the subscription_id column not existing.
Fix: Unable to update Stripe billing card if the subscription wasn't originally created by RCP.
Fix: CSV importer reporting incorrect row numbers after the first batch.

Fix: PHP 5.6 error due to use of type hinting.
Fix: Check if wp_is_site_initialized() exists before using to prevent errors in WordPress versions below 5.1.

New: Introduced new filter rcp_is_rcp_admin_page. RCP scripts and styles are enqueued when this returns true so third party plugins can use this filter to load RCP scripts and styles on their own pages.
Improvement: $_POST data is now available during rcp_validate_registration_state ajax action.
Fix: MySQL errors on multisite when switch_blog action runs for the first time after new sites are created but before the database tables are created.
Fix: If a customers database table upgrade runs a second time it throws an error.
Fix: Improve logic on Stripe subscription creation dates to better protect against failures with non-standard billing cycles.
Fix: Add checks in case the one_time column is missing from the discounts database table, and add it in if so. This error could occur when upgrading from a very old version.