PMPro_Member_Edit_Panel_Memberships.save incorrectly uses local timezone when saving membership start date

[kk-sonata]

Describe the bug
When an admin edits a user membership, PMPro saves the membership start date to the database using the server's local timezone. WordPress's current_time function returns the local time unless the $gmt argument is specified.
'startdate' => current_time( 'mysql' )

paid-memberships-pro/adminpages/member-edit/pmpro-class-member-edit-panel-memberships.php

Lines 757 to 771 in 6073625

	// Add the membership level.
	$level_to_add = array(
	'user_id' => $user->ID,
	'membership_id' => $level_id,
	'code_id' => '',
	'initial_payment' => 0,
	'billing_amount' => 0,
	'cycle_number' => 0,
	'cycle_period' => 'month',
	'billing_limit' => 0,
	'trial_amount' => 0,
	'trial_limit' => 0,
	'startdate' => current_time( 'mysql' ),
	'enddate' => empty( $expiration ) ? 'NULL' : date( 'Y-m-d H:i:s', strtotime( $expiration ) )
	);

However, when retrieving the start date function pmpro_getMemberStartdate assumes that the startdate in the DB is UTC (+00:00), and applies a TZ conversion to it. This causes an inaccurate startdate to be returned.

paid-memberships-pro/includes/functions.php

Lines 2865 to 2869 in 6073625

	if ( ! empty( $level_id ) ) {
	$sqlQuery = "SELECT UNIX_TIMESTAMP(CONVERT_TZ(startdate, '+00:00', @@global.time_zone)) FROM $wpdb->pmpro_memberships_users WHERE status = 'active' AND membership_id IN(" . (int) $level_id . ") AND user_id = '" . $user_id . "' ORDER BY id LIMIT 1";
	} else {
	$sqlQuery = "SELECT UNIX_TIMESTAMP(CONVERT_TZ(startdate, '+00:00', @@global.time_zone)) FROM $wpdb->pmpro_memberships_users WHERE status = 'active' AND user_id = '" . esc_sql( $user_id ) . "' ORDER BY id LIMIT 1";
	}

To Reproduce
Steps to reproduce the behavior:

1. Edit a user's PMPro membership level through the Wordpress dashboard
2. While logged in as the user, execute a snippet such as

	global $current_user;
	$startdate = pmpro_getMemberStartdate($current_user->ID);
	echo 'Membership start date: ' . date("Y-m-d H:i:s", $startdate) . '<br/>';

3. Incorrect start date will be returned

Expected behavior
Dates should be saved in the database as UTC, not local timezone

Isolating the problem (mark completed items with an [x]):

• I have deactivated other plugins and confirmed this bug occurs when only Paid Memberships Pro plugin is active.
• This bug happens with a default WordPress theme active, or Memberlite.
• I can reproduce this bug consistently using the steps above.

WordPress Environment

Details

Wordpress 6.8.1 PHP 8.2.28 PMPro 3.4.6