feat: add pg_partman container image

pg_partman is a PostgreSQL extension for automated table partition management.
It supports both time-based and ID-based partitioning with automatic creation
and maintenance of child tables. The background worker (pg_partman_bgw) can
automatically run partition maintenance at configured intervals, removing the
need for external cron jobs.

Closes #205

Signed-off-by: Kristiansen, Erling Gustav Moland <Erling.Kristiansen@skatteetaten.no>

Author: Kristiansen, Erling Gustav Moland

pg-partman/Dockerfile

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+# SPDX-FileCopyrightText: Copyright © contributors to CloudNativePG, established as CloudNativePG a Series of LF Projects, LLC.
+# SPDX-License-Identifier: Apache-2.0
+
+ARG BASE=ghcr.io/cloudnative-pg/postgresql:18-minimal-trixie
+FROM $BASE AS builder
+
+ARG PG_MAJOR
+ARG EXT_VERSION
+
+USER 0
+
+# Install extension via `apt-get`
+RUN apt-get update && apt-get install -y --no-install-recommends \
+      "postgresql-${PG_MAJOR}-partman=${EXT_VERSION}"
+
+FROM scratch
+ARG PG_MAJOR
+
+# Licenses
+COPY --from=builder /usr/share/doc/postgresql-${PG_MAJOR}-partman/copyright /licenses/postgresql-${PG_MAJOR}-partman/
+
+# Libraries
+COPY --from=builder /usr/lib/postgresql/${PG_MAJOR}/lib/pg_partman_bgw.so /lib/
+COPY --from=builder /usr/lib/postgresql/${PG_MAJOR}/lib/bitcode/ /lib/bitcode/
+
+# Share
+COPY --from=builder /usr/share/postgresql/${PG_MAJOR}/extension/pg_partman* /share/extension/
+
+# Binaries (maintenance scripts)
+COPY --from=builder /usr/lib/postgresql/${PG_MAJOR}/bin/check_unique_constraint.py /bin/
+COPY --from=builder /usr/lib/postgresql/${PG_MAJOR}/bin/dump_partition.py /bin/
+COPY --from=builder /usr/lib/postgresql/${PG_MAJOR}/bin/vacuum_maintenance.py /bin/
+
+USER 65532:65532

pg-partman/README.md

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+# pg_partman
+<!--
+SPDX-FileCopyrightText: Copyright © contributors to CloudNativePG, established as CloudNativePG a Series of LF Projects, LLC.
+SPDX-License-Identifier: Apache-2.0
+-->
+
+[pg_partman](https://github.com/pgpartman/pg_partman) is a PostgreSQL extension
+for automated table partition management. It supports both time-based and
+ID-based partitioning with automatic creation and maintenance of child tables.
+
+The extension includes a background worker (`pg_partman_bgw`) that can
+automatically run partition maintenance at configured intervals, removing the
+need for external cron jobs.
+
+For more information, see the
+[official documentation](https://github.com/pgpartman/pg_partman).
+
+## Usage
+
+The `pg_partman` extension must be loaded via `shared_preload_libraries` to
+enable the background worker. The worker periodically runs
+`partman.run_maintenance_proc()` to create new partitions and drop expired ones.
+
+### 1. Add the pg_partman extension image to your Cluster
+
+Define the `pg-partman` extension under the `postgresql.extensions` section of
+your `Cluster` resource. For example:
+
+```yaml
+apiVersion: postgresql.cnpg.io/v1
+kind: Cluster
+metadata:
+  name: cluster-pg-partman
+spec:
+  imageName: ghcr.io/cloudnative-pg/postgresql:18-minimal-trixie
+  instances: 1
+
+  storage:
+    size: 1Gi
+
+  postgresql:
+    shared_preload_libraries:
+    - pg_partman_bgw
+    extensions:
+    - name: pg-partman
+      image:
+        # renovate: suite=trixie-pgdg depName=postgresql-18-partman
+        reference: ghcr.io/cloudnative-pg/pg-partman:5.4.3-18-trixie
+```
+
+### 2. Enable the extension in a database
+
+You can install `pg_partman` in a specific database by creating or updating a
+`Database` resource. For example, to enable it in the `app` database:
+
+```yaml
+apiVersion: postgresql.cnpg.io/v1
+kind: Database
+metadata:
+  name: cluster-pg-partman-app
+spec:
+  name: app
+  owner: app
+  cluster:
+    name: cluster-pg-partman
+  extensions:
+  - name: pg_partman
+    # renovate: suite=trixie-pgdg depName=postgresql-18-partman
+    version: '5.4.3'
+```
+
+### 3. Verify installation
+
+Once the database is ready, connect to it with `psql` and run:
+
+```sql
+\dx
+```
+
+You should see `pg_partman` listed among the installed extensions.
+
+## Included utilities
+
+This image also bundles the following Python maintenance scripts in `/bin/`:
+
+- `check_unique_constraint.py` — validates unique constraints across partitions
+- `dump_partition.py` — exports individual partitions for archival
+- `vacuum_maintenance.py` — targeted vacuum operations on partitioned tables
+
+> [!NOTE]
+> These scripts require a Python 3 runtime and the `psycopg2` library, which
+> are not included in the minimal base image. They are provided for
+> environments where Python is available on the host or in a sidecar container.
+
+## Contributors
+
+This extension is maintained by:
+
+- Erling Kristiansen (@egkristi)
+
+The maintainers are responsible for:
+
+- Monitoring upstream releases and security vulnerabilities.
+- Ensuring compatibility with supported PostgreSQL versions.
+- Reviewing and merging contributions specific to this extension's container
+  image and lifecycle.
+
+---
+
+## Licenses and Copyright
+
+This container image contains software that may be licensed under various
+open-source licenses.
+
+All relevant license and copyright information for the `pg_partman` extension
+and its dependencies are bundled within the image at:
+
+```text
+/licenses/
+```
+
+By using this image, you agree to comply with the terms of the licenses
+contained therein.

pg-partman/metadata.hcl

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+# SPDX-FileCopyrightText: Copyright © contributors to CloudNativePG, established as CloudNativePG a Series of LF Projects, LLC.
+# SPDX-License-Identifier: Apache-2.0
+metadata = {
+  name                     = "pg-partman"
+  sql_name                 = "pg_partman"
+  image_name               = "pg-partman"
+  licenses                 = ["PostgreSQL"]
+  shared_preload_libraries = ["pg_partman_bgw"]
+  postgresql_parameters    = {}
+  extension_control_path   = []
+  dynamic_library_path     = []
+  ld_library_path          = []
+  bin_path                 = ["bin"]
+  env                      = {}
+  auto_update_os_libs      = false
+  required_extensions      = []
+  create_extension         = true
+
+  versions = {
+    bookworm = {
+      "18" = {
+        // renovate: suite=bookworm-pgdg depName=postgresql-18-partman
+        package = "5.4.3-1.pgdg12+1"
+        // renovate: suite=bookworm-pgdg depName=postgresql-18-partman extractVersion=^(?<version>\d+\.\d+\.\d+)
+        sql     = "5.4.3"
+      }
+    }
+    trixie = {
+      "18" = {
+        // renovate: suite=trixie-pgdg depName=postgresql-18-partman
+        package = "5.4.3-1.pgdg13+1"
+        // renovate: suite=trixie-pgdg depName=postgresql-18-partman extractVersion=^(?<version>\d+\.\d+\.\d+)
+        sql     = "5.4.3"
+      }
+    }
+  }
+}