Make the vault injection serviceAccount name a configuration option

Is your feature request related to a problem? Please describe.
Our Kubernetes cluster is configured to use a mandated and dedicated pod security policy service account for all deployments, statefulsets, psp and role bindings, and cluster role bindings. The current helm-vault version has a configuration option for the server (statefulset) service account , but not for the injector service account.

pod/vault-0                    1/1     Running   0          67m
pod/vault-1                    1/1     Running   0          67m
pod/vault-2                    1/1     Running   0          67m

NAME                                   READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/vault-agent-injector   0/1     0            0           67m

As you can see, the vault-agent-injector is in an un-ready state since the injector binding resources use a hardcoded service account for the vault agent injector, which further has no access in the cluster. Therefore, all injections fail. My only option here is to download the latest vault-hrlm branch/tags, edit the template files, and install. This is a cumbersome approach in our CI/CD pipelines for every news version since I must check out the repo locally and tweak the files. I want to be able to use helm repo add and helm install with a custom values file, also when PSP is imposed in the cluster for service accounts.

Describe the solution you'd like
The solution is to do a similar update as implemented for the server.serviceaccount, e.g updating the files _helpers.tpl, injector-serviceaccount.yaml, injector-deployment.yaml, injector-clusterrolebinding.yaml and injector-psp-rolebinding.yaml

# File: values-custom.yaml
injector:
  serviceAccount:
    create: false
    name: "namespacename-restricted-osname"

# File: values.yaml
injector:
  serviceAccount:
    create: true
    name: ""

# File: _helpers.tpl
{{- define "vault.injector.serviceAccount.name" -}}
{{- if .Values.injector.serviceAccount.create -}}
    {{ default (include "vault.fullname" .) . "-agent-injector" }}
{{- else -}}
    {{ default "default" .Values.injector.serviceAccount.name }}
{{- end -}}
{{- end -}}

# File : injector-clusterrolebinding
subjects:
- kind: ServiceAccount
  name: {{ template "vault.injector.serviceAccount.name" . }}

# File: injector-deployment.yaml
spec
  template:
    spec::
      serviceAccountName: {{ template "vault.injector.serviceAccount.name" . }}

# File: injector-psp-rolebinding.yaml
subjects:
- kind: ServiceAccount
  name: {{ template "vault.injector.serviceAccount.name" . }}

#File: injector-serviceaccount.yaml
{{- if (eq (.Values.injector.serviceAccount.create | toString) "true" ) }}
metadata:
  name: {{ template "vault.injector.serviceAccount.name" . }}
  labels:
    app.kubernetes.io/name: {{ template "vault.injector.serviceAccount.name" . }}
{{ end }}

Start by comparing the existing server.serviceaccount configuration in _helpers.tpl and the injector templates named in the issue: injector-serviceaccount.yaml, injector-deployment.yaml, injector-clusterrolebinding.yaml, and injector-psp-rolebinding.yaml. Verify the chart with a custom values file where injector.serviceAccount.create and name are set, and confirm the injector deployment and bindings use the configured account.