client: export types implementing CallOptions for access by interceptors (#1902)

call.go

@@ -27,6 +27,10 @@ import (
 //
 // All errors returned by Invoke are compatible with the status package.
 func (cc *ClientConn) Invoke(ctx context.Context, method string, args, reply interface{}, opts ...CallOption) error {
+	// allow interceptor to see all applicable call options, which means those
+	// configured as defaults from dial option as well as per-call options
+	opts = append(cc.dopts.callOptions, opts...)
+
 	if cc.dopts.unaryInt != nil {
 		return cc.dopts.unaryInt(ctx, method, args, reply, cc, invoke, opts...)
 	}