doc: organize and add missing E2E tests in End-to-End Tests section. (cloudnative-pg#945)

Closes cloudnative-pg#943

Signed-off-by: Jitendra Wadle <jitendra.wadle@enterprisedb.com>
Signed-off-by: Armando Ruocco <armando.ruocco@enterprisedb.com>
Signed-off-by: Jaime Silvela <jaime.silvela@enterprisedb.com>
Co-authored-by: Armando Ruocco <armando.ruocco@enterprisedb.com>
Co-authored-by: Jaime Silvela <jaime.silvela@enterprisedb.com>

Author: 3 people

docs/src/e2e.md

@@ -1,12 +1,11 @@
 # End-to-End Tests
 
-CloudNativePG operator is automatically tested after each
-commit via a suite of **End-to-end (E2E) tests**. It ensures that
-the operator correctly deploys and manages the PostgreSQL clusters.
+CloudNativePG is automatically tested after each
+commit via a suite of **End-to-end (E2E) tests**, which ensures that
+the operator correctly deploys and manages PostgreSQL clusters.
 
 Moreover, the following Kubernetes versions are tested for each commit,
-ensuring failure and bugs detection at an early stage of the development
-process:
+helping detect bugs at an early stage of the development process:
 
 * 1.25
 * 1.24
@@ -16,7 +15,7 @@ process:
 
 The following PostgreSQL versions are tested:
 
-* PostgreSQL 15 beta (**not for production!!!**)
+* PostgreSQL 15
 * PostgreSQL 14
 * PostgreSQL 13
 * PostgreSQL 12
@@ -27,34 +26,66 @@ For each tested version of Kubernetes and PostgreSQL, a Kubernetes
 cluster is created using [kind](https://kind.sigs.k8s.io/),
 and the following suite of E2E tests are performed on that cluster:
 
-* Installation of the operator;
-* Creation of a `Cluster`;
-* Usage of a persistent volume for data storage;
-* Connection via services, including read-only;
-* Connection via user-provided server and/or client certificates;
-* Scale-up and scale-down of a `Cluster`;
-* Failover;
-* Switchover;
-* Manage PostgreSQL configuration changes;
-* Rolling updates when changing PostgreSQL images;
-* Backup and ScheduledBackups execution;
-* Backup and ScheduledBackups execution using Barman Cloud on Azure blob storage;
-* Synchronous replication;
-* Restore from backup;
-* Restore from backup using Barman Cloud on Azure blob storage;
-* Pod affinity using `NodeSelector`;
-* Metrics collection;
-* JSON log format;
-* Operator configuration via ConfigMap;
-* Operator pod deletion;
-* Operator pod eviction;
-* Operator upgrade;
-* Operator High Availability;
-* Node drain;
-* Primary endpoint switch in case of failover in less than 10 seconds;
-* Primary endpoint switch in case of switchover in less than 20 seconds;
-* Recover from a degraded state in less than 60 seconds;
-* Physical replica clusters;
-* Storage expansion;
-* Data corruption;
-* Replication Slots;
+- **Basic:**
+    * Installation of the operator;
+    * Creation of a Cluster;
+    * Usage of a persistent volume for data storage;
+- **Service connectivity:**
+    * Connection via services, including read-only;
+    * Connection via user-provided server and/or client certificates;
+    * PgBouncer;
+- **Self-healing:**
+    * Failover;
+    * Switchover;
+    * Primary endpoint switch in case of failover in less than 10 seconds;
+    * Primary endpoint switch in case of switchover in less than 20 seconds;
+    * Recover from a degraded state in less than 60 seconds;
+    * PVC Deletion;
+- **Backup and Restore:**
+    * Backup and ScheduledBackups execution using Barman Cloud on S3;
+    * Backup and ScheduledBackups execution using Barman Cloud on Azure
+    blob storage;
+    * Restore from backup using Barman Cloud on S3;
+    * Restore from backup using Barman Cloud on Azure blob storage;
+    * Wal-Restore;
+- **Operator:**
+    * Operator Deployment;
+    * Operator configuration via ConfigMap;
+    * Operator pod deletion;
+    * Operator pod eviction;
+    * Operator upgrade;
+    * Operator High Availability;
+- **Observability:**
+    * Metrics collection;
+    * PgBouncer Metrics;
+    * JSON log format;
+- **Replication:**
+    * Physical replica clusters;
+    * Replication Slots;
+    * Synchronous replication;
+    * Scale-up and scale-down of a Cluster;
+- **Plugin:**
+    * Cluster Hibernation using CNPG plugin;
+    * Fencing;
+    * Creation of a connection certificate;
+- **Postgres Configuration:**
+    * Manage PostgreSQL configuration changes;
+    * Rolling updates when changing PostgreSQL images;
+- **Pod Scheduling:**
+    * Tolerations and taints;
+    * Pod affinity using `NodeSelector`;
+- **Cluster Metadata:**
+    * ConfigMap for Cluster Labels and Annotations;
+    * Object metadata;
+- **Recovery:**
+    * Data corruption;
+    * pg_basebackup;
+- **Importing Databases:**
+    * Microservice approach;
+    * Monolith approach;
+- **Storage:**
+    * Storage expansion;
+- **Security:**
+    * AppArmor annotation propagation. Executed only on Azure environment;
+- **Maintenance:**
+    * Node Drain;