This feature allows you to mount a PostgreSQL extension, packaged as an OCI-compliant container image, as a read-only, immutable volume inside an instance pod.

The new .spec.postgresql.extensions stanza of a Cluster resource accepts an ordered list of extension images to be added to the PostgreSQL cluster. Each item in the extensions stanza is identified by name and provides the following options:

• extension_control_path: A list of relative paths within the container image to be appended to PostgreSQL’s extension_control_path, allowing it to locate extension control files (default: share).
• dynamic_library_path: A list of relative paths within the container image to be appended to PostgreSQL’s dynamic_library_path, enabling it to locate shared library files for extensions (default: lib).
• ld_library_path: A list of relative paths within the container image to be appended to the LD_LIBRARY_PATH environment variable of the instance manager process, allowing PostgreSQL to locate required system libraries at runtime (default: empty).

Each image volume is mounted at /extensions/<EXTENSION_NAME>. By default, CloudNativePG automatically manages the relevant PostgreSQL GUCs, setting:

• extension_control_path to /extensions/<EXTENSION_NAME>/share, allowing PostgreSQL to locate any extension control file within /extensions/<EXTENSION_NAME>/share/extension
• dynamic_library_path to /extensions/<EXTENSION_NAME>/lib

These values are appended in the order in which the extensions are defined in the extensions list, ensuring deterministic path resolution within PostgreSQL.

Requirements:

• PostgreSQL 18 or higher (for the extension_control_path option)
• Kubernetes 1.33+ with the ImageVolume feature enabled

Closes #7188