feat(restheadspec): add x-searchop-notcontain operator

Maps notcontain/notcontains/notlike to a not_ilike filter rendered as
(col IS NULL OR CAST(col AS TEXT) NOT ILIKE ?), so NULL rows are kept.

pkg/common/json_condition.go

@@ -139,6 +139,10 @@ func BuildJSONFilterCondition(model interface{}, tableAlias, token, operator str
 		return fmt.Sprintf("%s LIKE ?", colExpr), prepend(value), true
 	case "ilike":
 		return fmt.Sprintf("%s ILIKE ?", colExpr), prepend(value), true
+	case "not_ilike":
+		// colExpr appears twice, so its bound args must be repeated too.
+		notArgs := append(append([]interface{}{}, colArgs...), colArgs...)
+		return fmt.Sprintf("(%s IS NULL OR %s NOT ILIKE ?)", colExpr, colExpr), append(notArgs, value), true
 	case "in":
 		inCond, inArgs := BuildInCondition(colExpr, value)
 		if inCond == "" {

pkg/common/json_condition_test.go

@@ -93,6 +93,11 @@ func TestBuildJSONFilterCondition(t *testing.T) {
 			wantCond: `("data" #>> ?::text[]) ILIKE ?`,
 			wantArgs: []interface{}{"{city}", "%la%"},
 		},
+		{
+			name: "not_ilike repeats bound path", token: "data->>'city'", operator: "not_ilike", value: "%la%",
+			wantCond: `(("data" #>> ?::text[]) IS NULL OR ("data" #>> ?::text[]) NOT ILIKE ?)`,
+			wantArgs: []interface{}{"{city}", "{city}", "%la%"},
+		},
 		{
 			name: "in", token: "data->>'tier'", operator: "in", value: []string{"a", "b"},
 			wantCond: `("data" #>> ?::text[]) IN (?,?)`,