feat: Update to OPA v1.2.0 (#373)

Regorus now defaults to rego v1. `import rego.v1` is no longer needed.
Additionally, `future` keywords are automatically imported.

See
https://www.openpolicyagent.org/docs/latest/v0-upgrade/#changes-to-rego-in-opa-v10
to understand the differences between rego v1 and v0.

BREAKING CHANGE:

v0 style policies will error out by default. To enable v0 behavior, call engine.set_rego_v0(true) before
loading policies.

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

bindings/go/pkg/regorus/mod.go

@@ -28,6 +28,17 @@ func (e *Engine) Clone() *Engine {
 	return c
 }
 
+func (e *Engine) SetRegoV0(enable bool) (error) {
+	result := C.regorus_engine_set_rego_v0(e.e, C.bool(enable))
+	defer C.regorus_result_drop(result)
+
+	if result.status != C.RegorusStatusOk {
+		return fmt.Errorf("%s", C.GoString(result.error_message))
+	}
+
+	return nil
+}
+
 func (e *Engine) AddPolicy(path string, rego string) (string, error) {
 	path_c := C.CString(path)
 	defer C.free(unsafe.Pointer(path_c))