Operator Crashes when securityContext is empty

[theSuess]

When specifying an empty security context in the Tenant, the logic introduced in #1372 crashes with a nil pointer dereference.

Having an empty object as securityContext is especially useful/required on OpenShift where the securityContext is dynamically injected.

Expected Behavior

• Specifying .spec.pools[].securityContext: {} should not crash the operator

Current Behavior

• The operator crashes. Stack trace

github.com/minio/operator/pkg/resources/statefulsets.poolContainerSecurityContext(...)
github.com/minio/operator/pkg/resources/statefulsets/minio-statefulset.go:414
github.com/minio/operator/pkg/resources/statefulsets.poolMinioServerContainer(_, _, _, _, {_, _}, {_, _}, _, {0xc00360eba0, ...})
github.com/minio/operator/pkg/resources/statefulsets/minio-statefulset.go:347 +0x40d
github.com/minio/operator/pkg/resources/statefulsets.NewPool(0xc0022be000, 0x0?, 0x0?, 0xc0033a5420, 0x0?, {0xc000f38c70, 0xd}, {0x0, 0x0}, {0x1f155fc, ...}, ...)
github.com/minio/operator/pkg/resources/statefulsets/minio-statefulset.go:769 +0x2dc5
github.com/minio/operator/pkg/controller/cluster.(*Controller).syncHandler(0xc000326900, {0xc0035b1820, 0x1c})
github.com/minio/operator/pkg/controller/cluster/main-controller.go:1156 +0x45ea
github.com/minio/operator/pkg/controller/cluster.(*Controller).processNextWorkItem.func1({0x1926b00?, 0xc004238d00})
github.com/minio/operator/pkg/controller/cluster/main-controller.go:605 +0x24f
github.com/minio/operator/pkg/controller/cluster.(*Controller).processNextWorkItem(0xc000326900)
github.com/minio/operator/pkg/controller/cluster/main-controller.go:617 +0x62
github.com/minio/operator/pkg/controller/cluster.(*Controller).runWorker(0xc000a5cea0?)
github.com/minio/operator/pkg/controller/cluster/main-controller.go:557 +0x47

Possible Solution

The offending code assumes a few securitycontext fields to be set. We need to check for their existance before accessing: https://github.com/minio/operator/blob/v4.5.6/pkg/resources/statefulsets/minio-statefulset.go#L414

Steps to Reproduce (for bugs)

1. Setup the Operator in version 4.5.6
2. Create a tenant with a pool containing securityContext: {}
3. Observe the crash

Context

This has broken the minio operator on two clusters now. Together with #1234 this makes the Operator unusable on OpenShift

Your Environment

• Version used (minio-operator): 4.5.6
• Environment name and version: v1.24.6+5658434/OpenShift 4.11.18

[pjuarezd]

This should be resolved in starting 5.0.0, current release (Operator 5.0.3) included.
This allows security context to be empty.