Strip api-injected empty overrides from dashboard state

Amp-Thread-ID: https://ampcode.com/threads/T-019c9bc7-a165-774f-b025-2e92d6e0b9d5
Co-authored-by: Amp <amp@ampcode.com>

Author: toppercodes

axiom/resource_dashboard.go

@@ -461,6 +461,14 @@ func normalizeDashboardRaw(raw json.RawMessage, configured types.String) (string
 		delete(parsed, "uid")
 	}
 
+	if overrides, ok := parsed["overrides"]; ok && isEmptyMap(overrides) {
+		if !hasConfiguredMap {
+			delete(parsed, "overrides")
+		} else if _, configuredHasOverrides := configuredMap["overrides"]; !configuredHasOverrides {
+			delete(parsed, "overrides")
+		}
+	}
+
 	normalized, err := json.Marshal(parsed)
 	if err != nil {
 		return "", err
@@ -510,6 +518,15 @@ func stringValueFromMap(in map[string]any, key string) (string, bool) {
 	return s, true
 }
 
+func isEmptyMap(v any) bool {
+	m, ok := v.(map[string]any)
+	if !ok {
+		return false
+	}
+
+	return len(m) == 0
+}
+
 func addDashboardUpdateError(resp *resource.UpdateResponse, err error, uid string, localVersion int64) {
 	addDashboardWriteErrorDiagnostics(&resp.Diagnostics, err, uid, localVersion)
 }

axiom/resource_dashboard_test.go

@@ -97,6 +97,32 @@ func TestNormalizeDashboardRaw_RemovesUnconfiguredTopLevelFields(t *testing.T) {
 	}
 }
 
+func TestNormalizeDashboardRaw_KeepsConfiguredOverrides(t *testing.T) {
+	got, err := normalizeDashboardRaw(
+		json.RawMessage(`{"name":"dashboard","overrides":{"series":[]}}`),
+		types.StringValue(`{"name":"dashboard","overrides":{"series":[]}}`),
+	)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if !strings.Contains(got, `"overrides"`) {
+		t.Fatalf("expected configured overrides to be preserved, got %s", got)
+	}
+}
+
+func TestNormalizeDashboardRaw_RemovesEmptyOverridesWhenConfigUnavailable(t *testing.T) {
+	got, err := normalizeDashboardRaw(
+		json.RawMessage(`{"name":"dashboard","overrides":{}}`),
+		types.StringNull(),
+	)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if strings.Contains(got, `"overrides"`) {
+		t.Fatalf("expected empty overrides to be removed, got %s", got)
+	}
+}
+
 func TestDashboardUpsertPayloadFromModel_CreateWithUID(t *testing.T) {
 	plan := DashboardResourceModel{
 		UID:       types.StringValue("uid_from_config"),