Define keyNames to backups.secrets

[ercpereda]

Hi, this is my first contribution so please let me know if I have missed anything.

This PR adds the posibility to define the name of the keys for the secret containing the credentials of the backups.

Fixes #383

[itay-grudev]

@ercpereda We require that you signoff on your commits? Can you please take a look at this: https://github.com/cloudnative-pg/charts/pull/384/checks?check_run_id=29909669764

[ercpereda]

@itay-grudev Thank you for the response. The commit is now signoff.

[ercpereda]

@itay-grudev Something else that can be done to get this merge? Thank you?

[itay-grudev]

A local negative gravitational anomaly. Something that accelerates time, but just in my frame of reference.

[jorgebsa]

This would be great to have, ran into this limitation when using an ObjectBucketClaim with storage class openshift-storage.noobaa.io, which prefixes the keys with AWS_ on the generated secret. Had to resort to FluxCD's HelmRelease's valuesFrom to pass the values to the chart

[itay-grudev]

@ercpereda Would you please be able to add a test for this in: https://github.com/cloudnative-pg/charts/tree/main/charts/cluster/test/postgresql-cluster-configuration

This tests whether non-default configuration properties get forwarded correctly and ensures we don't accidentally break something in the future.

[itay-grudev]

@ercpereda It also seems like there is a test failure:

Error: template: cluster/templates/cluster.yaml:103:5: executing "cluster/templates/cluster.yaml" at <include "cluster.bootstrap" .>: error calling include: template: cluster/templates/_bootstrap.tpl:90:10: executing "cluster.bootstrap" at <include "cluster.barmanObjectStoreConfig" $d>: error calling include: template: cluster/templates/_barman_object_store.tpl:28:104: executing "cluster.barmanObjectStoreConfig" at <.scope.secret.keyNames.accessKey>: nil pointer evaluating interface {}.accessKey