Do not use beast base64 encoding without fix:

Boost 1.67 and 1.68 are missing this fix
0439dcfa7a

src/test/rpc/ValidatorRPC_test.cpp

@@ -19,12 +19,12 @@
 
 #include <ripple/app/main/BasicApp.h>
 #include <ripple/app/misc/ValidatorSite.h>
+#include <ripple/basics/base64.h>
 #include <ripple/beast/unit_test.h>
 #include <ripple/core/ConfigSections.h>
 #include <ripple/json/json_value.h>
 #include <ripple/protocol/JsonFields.h>
 #include <ripple/protocol/Sign.h>
-#include <boost/beast/core/detail/base64.hpp>
 #include <test/jtx.h>
 #include <test/jtx/TrustedPublisherServer.h>
 
@@ -75,7 +75,7 @@ class ValidatorRPC_test : public beast::unit_test::suite
         Serializer s;
         st.add(s);
 
-        return boost::beast::detail::base64_encode(
+        return base64_encode(
             std::string(static_cast<char const*>(s.data()), s.size()));
     }