Releases for Pantheon Advanced Page Cache

Fix cache keys being cleared on install.php

This release is exactly the same than 1.3.

Only changes are:
- Drupal 8 support removed.
- Drupal 9.4 set as minimum supported Drupal version.

Fixes #2944229 When creating a new node view does not display the new node

This release adds Drupal 9 compatibility #3135416: Drupal 9 compatibility fixes for Pantheon Advanced Page Cache

Changes since beta1 are:

• Document debug header to get Surrogate-Key-Raw
  • This change was only an update to documentation to describe how to see the header information set by the module.
• Very large headers generate 502 error responses
  • Now instead of 502 errors, the module will trim the header and log a warning message.

Fixes #2940779. Testing dependencies had been in Composer's 'require' section instead of 'require-dev'.

Jumping from an Alpha to a Beta release tag to indicate growing confidence in the module's stability as more sites adopt it.

Removing "known issues" from readme file after fixes in Pantheon's internal API.

This release contains no changes in module code compared to Alpha1.