Merge pull request #28792 from hashicorp/b-cloudsearch-domain-service-access-policy

cloudsearch/domain_service_access_policy: Improve diff handling of policy

Author: YakDriver

.changelog/28792.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+resource/aws_cloudsearch_domain_service_access_policy: Improve refresh to avoid unnecessary diffs in `access_policy`
+```

internal/service/cloudsearch/domain_service_access_policy.go

@@ -34,10 +34,11 @@ func ResourceDomainServiceAccessPolicy() *schema.Resource {
 
 		Schema: map[string]*schema.Schema{
 			"access_policy": {
-				Type:             schema.TypeString,
-				Required:         true,
-				DiffSuppressFunc: verify.SuppressEquivalentPolicyDiffs,
-				ValidateFunc:     validation.StringIsJSON,
+				Type:                  schema.TypeString,
+				Required:              true,
+				DiffSuppressFunc:      verify.SuppressEquivalentPolicyDiffs,
+				DiffSuppressOnRefresh: true,
+				ValidateFunc:          validation.StringIsJSON,
 				StateFunc: func(v interface{}) string {
 					json, _ := structure.NormalizeJsonString(v)
 					return json