multiprocess: Add serialization code for vector<char>

src/test/ipc_test.capnp

@@ -16,4 +16,5 @@ interface FooInterface $Proxy.wrap("FooImplementation") {
     passOutPoint @1 (arg :Data) -> (result :Data);
     passUniValue @2 (arg :Text) -> (result :Text);
     passTransaction @3 (arg :Data) -> (result :Data);
+    passVectorChar @4 (arg :Data) -> (result :Data);
 }

src/test/ipc_test.cpp

@@ -97,6 +97,10 @@ void IpcPipeTest()
     CTransactionRef tx2{foo->passTransaction(tx1)};
     BOOST_CHECK(*Assert(tx1) == *Assert(tx2));
 
+    std::vector<char> vec1{'H', 'e', 'l', 'l', 'o'};
+    std::vector<char> vec2{foo->passVectorChar(vec1)};
+    BOOST_CHECK_EQUAL(std::string_view(vec1.begin(), vec1.end()), std::string_view(vec2.begin(), vec2.end()));
+
     // Test cleanup: disconnect pipe and join thread
     disconnect_client();
     thread.join();

src/test/ipc_test.h

@@ -16,6 +16,7 @@ public:
     COutPoint passOutPoint(COutPoint o) { return o; }
     UniValue passUniValue(UniValue v) { return v; }
     CTransactionRef passTransaction(CTransactionRef t) { return t; }
+    std::vector<char> passVectorChar(std::vector<char> v) { return v; }
 };
 
 void IpcPipeTest();