docs: add operator capability level and index

Signed-off-by: Gabriele Bartolini <[email protected]>

docs/src/database_import.md

@@ -267,3 +267,21 @@ topic is beyond the scope of CloudNativePG, we recommend that you reduce
 unnecessary writes in the checkpoint area by tuning Postgres GUCs like
 `shared_buffers`, `max_wal_size`, `checkpoint_timeout` directly in the
 `Cluster` configuration.
+
+## Online Import and Upgrades
+
+Logical replication offers a powerful way to import any PostgreSQL database
+accessible over the network using the following approach:
+
+- **Import Bootstrap with Schema-Only Option**: Initialize the schema in the
+  target database before replication begins.
+- **`Subscription` Resource**: Set up continuous replication to synchronize
+  data changes.
+
+This technique can also be leveraged for performing major PostgreSQL upgrades
+with minimal downtime, making it ideal for seamless migrations and system
+upgrades.
+
+For more details, including limitations and best practices, refer to the
+[Logical Replication](logical_replication.md) section in the documentation.
+

docs/src/index.md

@@ -96,12 +96,15 @@ Additionally, the community provides images for the [PostGIS extension](postgis.
 * In-place or rolling updates for operator upgrades
 * TLS connections and client certificate authentication
 * Support for custom TLS certificates (including integration with cert-manager)
-* Continuous WAL archiving to an object store (AWS S3 and S3-compatible, Azure Blob Storage, and Google Cloud Storage)
+* Continuous WAL archiving to an object store (AWS S3 and S3-compatible, Azure
+  Blob Storage, and Google Cloud Storage)
 * Backups on volume snapshots (where supported by the underlying storage classes)
 * Backups on object stores (AWS S3 and S3-compatible, Azure Blob Storage, and Google Cloud Storage)
 * Full recovery and Point-In-Time recovery from an existing backup on volume snapshots or object stores
 * Offline import of existing PostgreSQL databases, including major upgrades of PostgreSQL
-* Online import of existing PostgreSQL databases, including major upgrades of PostgreSQL, through PostgreSQL native logical replication (imperative, via the `cnpg` plugin)
+* Online import of existing PostgreSQL databases, including major upgrades of
+  PostgreSQL, through PostgreSQL native logical replication (declarative, via
+  the `Subscription` resource)
 * Fencing of an entire PostgreSQL cluster, or a subset of the instances in a declarative way
 * Hibernation of a PostgreSQL cluster in a declarative way
 * Support for quorum-based and priority-based Synchronous Replication

docs/src/operator_capability_levels.md

@@ -590,6 +590,15 @@ and makes the use of the underlying PostgreSQL resources more efficient.
 Instead of connecting directly to a PostgreSQL service, applications can now
 connect to the PgBouncer service and start reusing any existing connection.
 
+### Logical Replication
+
+CloudNativePG supports PostgreSQL's logical replication in a declarative manner
+using `Publication` and `Subscription` custom resource definitions.
+
+Logical replication is particularly useful together with the import facility
+for online data migrations (even from public DBaaS solutions) and major
+PostgreSQL upgrades.
+
 ## Level 4: Deep insights
 
 Capability level 4 is about *observability*: monitoring,