WooCommerce Subscriptions 6.9.0

* Tweak: Add placeholder explanation for the upcoming recurring report. PR#3655
* Tweak: Add a link to QuickForget.com in the IPN error notice. PR#3744
* Fix: Fix COD gateway availability for trial subscriptions. PR#3740
* Fix: Fetch customer error notice messages on the change payment method page in WC post 3.9 version compatible way. PR#3730
* Fix: Don't reduce stock for items added to a subscription manually via admin screen. PR#3725
* Fix: Only display the automatic renewal note in emails when there's a next payment. PR#3679
* Fix: Use the interval to calculate first payment date for synced products. Fixes an issue that caused a purchase outside the sync grace period to not account for the subscription interval. PR#3303
* Dev: Add two new action hooks before and after change payment submit button. PR#3718
* Dev: Add a new helper function wcs_trial_has_passed(). PR#3289
* Dev: Replace uses of cal_days_in_month() with a date() equivalent. PR#3734
* Dev: Make various changes to improve coding standards. PRs#3748, #3749, #3753

* Fix: Ensure the mixed checkout setting correctly prevents mixed carts after customer login. PR#3696
* Fix: Translate the automatic subscription recurring note in emails. PR#3684
* Fix: Account for limited coupon use across recurring carts. Fixes an issue which leads to limited coupons applying beyond the limit. PR#3552
* Fix: Copy the item usage limit to coupons applied to manual renewal carts. PR#3686
* Dev: Add a filter to control access to the early renewal modal. PR#3675

* Fix: Save changes to payment method meta on the edit subscription screen. PR#3666
* Fix: Grant Shop Managers edit capabilities over subscriber users. PR#3669
* Fix: Remove original item from switched subscription during a multiple line item, different billing schedule switch. PR#3659
* Fix: Use strict conditionals when comparing results of as_next_scheduled_action. Fixes rescheduling of actions which were ran manually. PR#3661
* Tweak: To comply with Visa's changes to rules governing free trial subscriptions, add additional subscription details to email templates. PR#3664