This will set up a continuous wal streaming cluster, by adding the corresponding section in postgres manifest. Instead of having a full-fledged standby cluster as in Patroni, here we use only the wal path of the source cluster and stream from there.
Since, standby cluster is streaming from the master and does not require to create or use databases of it's own. Hence, it bypasses the creation of users or databases.
There is a separate sample manifest added to set up a standby-cluster.
* StatefulSet fsGroup config option to allow non-root spilo
* Allow Postgres CRD to overide SpiloFSGroup of the Operator.
* Document FSGroup of a Pod cannot be changed after creation.
Add possibility to mount a tmpfs volume to /dev/shm to avoid issues like
[this](https://github.com/docker-library/postgres/issues/416). To achieve that
two new options were introduced:
* `enableShmVolume` to PostgreSQL manifest, to specify whether or not mount
this volume per database cluster
* `enable_shm_volume` to operator configuration, to specify whether or not mount
per operator.
The first one, `enableShmVolume` takes precedence to allow us to be more flexible.
* Allow configuring pod priority globally and per cluster.
Allow to specify pod priority class for all pods managed by the operator,
as well as for those belonging to individual clusters.
Controlled by the pod_priority_class_name operator configuration
parameter and the podPriorityClassName manifest option.
See https://kubernetes.io/docs/concepts/configuration/pod-priority-preemption/#priorityclass
for the explanation on how to define priority classes since Kubernetes 1.8.
Some import order changes are due to go fmt.
Removal of OrphanDependents deprecated field.
Code review by @zerg-junior
* Define sidecars in the operator configuration.
Right now only the name and the docker image can be defined, but with
the help of the pod_environment_configmap parameter arbitrary
environment variables can be passed to the sidecars.
* Refactoring around generatePodTemplate.
Original implementation of per-cluster sidecars by @theRealWardo
Per review by @zerg-junior and @Jan-M