Allow non readOnly CSI additionalVolumes (#937)

### Description
Allow additionalVolumes with flag `readOnly: false` as per CSI setting.
Currently, all CSI driver volumes are hardcoded to `readOnly: true`

### Issues Resolved
Closing:
#934

### Check List
- [x] Commits are signed per the DCO using --signoff 
- [x] Unittest added for the new/changed functionality and all unit
tests are successful
- [ ] Customer-visible features documented (not applicable)
- [x] No linter warnings (`make lint`)

If CRDs are changed:  (not applicable)
- [ ] CRD YAMLs updated (`make manifests`) and also copied into the helm
chart
- [ ] Changes to CRDs documented

Please refer to the [PR
guidelines](https://github.com/opensearch-project/opensearch-k8s-operator/blob/main/docs/developing.md#submitting-a-pr)
before submitting this pull request.

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and
signing off your commits, please check
[here](https://github.com/opensearch-project/OpenSearch/blob/main/CONTRIBUTING.md#developer-certificate-of-origin).

Signed-off-by: Roman Krewer <roman.krewer.rk@gmail.com>

opensearch-operator/pkg/reconcilers/util/util.go

@@ -128,6 +128,9 @@ func CreateAdditionalVolumes(
 			})
 		}
 		if volumeConfig.CSI != nil {
+			if volumeConfig.CSI.ReadOnly != nil {
+				readOnly = *volumeConfig.CSI.ReadOnly
+			}
 			retVolumes = append(retVolumes, corev1.Volume{
 				Name: volumeConfig.Name,
 				VolumeSource: corev1.VolumeSource{

opensearch-operator/pkg/reconcilers/util/util_test.go

@@ -89,7 +89,7 @@ var _ = Describe("Additional volumes", func() {
 		})
 	})
 
-	When("CSI volume is added", func() {
+	When("CSI readOnly volume is added", func() {
 		It("Should have CSIVolumeSource fields", func() {
 			readOnly := true
 			volumeConfigs[0].CSI = &v1.CSIVolumeSource{
@@ -111,6 +111,28 @@ var _ = Describe("Additional volumes", func() {
 		})
 	})
 
+	When("CSI read-write volume is added", func() {
+		It("Should have CSIVolumeSource fields", func() {
+			readOnly := false
+			volumeConfigs[0].CSI = &v1.CSIVolumeSource{
+				Driver:   "testDriver",
+				ReadOnly: &readOnly,
+				VolumeAttributes: map[string]string{
+					"secretProviderClass": "testSecretProviderClass",
+				},
+				NodePublishSecretRef: &v1.LocalObjectReference{
+					Name: "testSecret",
+				},
+			}
+
+			volume, _, _, _ := CreateAdditionalVolumes(mockClient, namespace, volumeConfigs)
+			Expect(volume[0].CSI.Driver).To(Equal("testDriver"))
+			Expect(*volume[0].CSI.ReadOnly).Should(BeFalse())
+			Expect(volume[0].CSI.VolumeAttributes["secretProviderClass"]).To(Equal("testSecretProviderClass"))
+			Expect(volume[0].CSI.NodePublishSecretRef.Name).To(Equal("testSecret"))
+		})
+	})
+
 	When("CSI volume is added with subPath", func() {
 		It("Should have the subPath", func() {
 			volumeConfigs[0].CSI = &v1.CSIVolumeSource{}