dns v2 - both empty string and default should be allowed for namespace and partition in CE

.changelog/21230.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+dns: new version was not supporting partition or namespace being set to 'default' in CE version.
+```

agent/discovery/query_fetcher_v1.go

@@ -424,6 +424,7 @@ RPC:
 }
 
 func (f *V1DataFetcher) ValidateRequest(_ Context, req *QueryPayload) error {
+	f.logger.Debug(fmt.Sprintf("req %+v", req))
 	if req.EnableFailover {
 		return ErrNotSupported
 	}

agent/discovery/query_fetcher_v1_ce.go

@@ -15,7 +15,7 @@ func (f *V1DataFetcher) NormalizeRequest(req *QueryPayload) {
 }
 
 func validateEnterpriseTenancy(req QueryTenancy) error {
-	if req.Namespace != "" || req.Partition != acl.DefaultPartitionName {
+	if !(req.Namespace == "" || req.Namespace == acl.DefaultNamespaceName) || !(req.Partition == acl.DefaultPartitionName || req.Partition == "default") {
 		return ErrNotSupported
 	}
 	return nil

agent/discovery/query_fetcher_v1_ce_test.go

@@ -5,7 +5,60 @@
 
 package discovery
 
+import (
+	"github.com/stretchr/testify/require"
+	"testing"
+)
+
 const (
 	defaultTestNamespace = ""
 	defaultTestPartition = ""
 )
+
+func Test_validateEnterpriseTenancy(t *testing.T) {
+	testCases := []struct {
+		name     string
+		req      QueryTenancy
+		expected error
+	}{
+		{
+			name: "empty namespace and partition returns no error",
+			req: QueryTenancy{
+				Namespace: defaultTestNamespace,
+				Partition: defaultTestPartition,
+			},
+			expected: nil,
+		},
+		{
+			name: "namespace and partition set to 'default' returns no error",
+			req: QueryTenancy{
+				Namespace: "default",
+				Partition: "default",
+			},
+			expected: nil,
+		},
+		{
+			name: "namespace set to something other than empty string or `default` returns not supported error",
+			req: QueryTenancy{
+				Namespace: "namespace-1",
+				Partition: "default",
+			},
+			expected: ErrNotSupported,
+		},
+		{
+			name: "partition set to something other than empty string or `default` returns not supported error",
+			req: QueryTenancy{
+				Namespace: "default",
+				Partition: "partition-1",
+			},
+			expected: ErrNotSupported,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			err := validateEnterpriseTenancy(tc.req)
+			require.Equal(t, tc.expected, err)
+		})
+	}
+}