ObjectStorageS3Secret field is immutable

Version
Pulp operator v1.0.0-beta.1, Image quay.io/pulp/pulp-operator@sha256:ab39229f535d6eaeaa7502e39581ba0c89319400512ac51f99ee8b905449b617

Pulp version is 3.32

Describe the bug
I was trying to update the ObjectStorageS3Secret field (or object_storage_s3_secret in json representation),
as we wanted to move to a new S3 bucket

To Reproduce
Steps to reproduce the behavior:

1. Create Pulp resource with valid object_storage_s3_secret defined. We did so via ArgoCD, but any other means should also work
2. Update the object_storage_s3_secret to a new value with another valid secret pointing to an S3 configuration and apply that change to the cluster.

Expected behavior
The secret is updated and the settings.py is re-rendered. Best case would be that the pods would get restarted to pick up the new settings.py

Actual Behavior
The following error occurs:

2023-09-25T14:50:34Z	ERROR	repo_manager/utils.go:177	Could not update ObjectStorageS3Secret field	{"error": "ObjectStorageS3Secret field is immutable"}

Afterwards the update is reverted and ArgoCD shows the cluster state as out of sync.

Additional context
This is caused by this function. I'm not sure how exactly the logic behind the immutability works, but I think this field should not be immutable

Start in controllers/repo_manager/utils.go around the function near line 158 that rejects ObjectStorageS3Secret changes. Reproduce the update with two valid S3 secrets, then trace how settings.py is rendered and determine the intended update behavior, including whether pods need restarting; add coverage for the accepted behavior.