4.6.0

Changed

• Added X-Api-User-Agent header. (b3f685d)

Composer

• Changed php from >=7.4 to >=8.0.
• Changed wp-pay/core from ^4.15 to v4.16.0.
  Release notes: https://github.com/pronamic/wp-pay-core/releases/tag/v4.16.0