QOlmExpected and associated refactoring

As mentioned in the commit introducing `Expected`, `QOlmExpected` is
simply an alias for `Expected<T, QOlmError>`. This simplifies quite
a few function signatures in `QOlm*` classes and collapses unwieldy
`std::holds_alternative<>`/`std::get<>` constructs into a neat
contextual bool cast and an invocation of `operator*` or
`value()`/`error()` accessors that don't need to specify the type.

While refactoring the code, I found a couple of cases of mismatching
`uint32_t` and `qint32_t` in return values; a couple of cases where
`decrypt()` returns `QString` which is in fact `QByteArray` (e.g., in
`QOlmSession::decrypt()`); there's a repetitive algorithm in
`Connection::Private::sessionDecryptPrekey()` and
`sessionDecryptGeneral()`

1 files changed, 2 insertions, 3 deletions

diff --git a/autotests/testolmaccount.cpp b/autotests/testolmaccount.cpp
index 9989665a..e31ff6d3 100644
--- a/autotests/testolmaccount.cpp
+++ b/autotests/testolmaccount.cpp
@@ -21,7 +21,7 @@ void TestOlmAccount::pickleUnpickledTest()
     QOlmAccount olmAccount(QStringLiteral("@foo:bar.com"), QStringLiteral("QuotientTestDevice"));
     olmAccount.createNewAccount();
     auto identityKeys = olmAccount.identityKeys();
-    auto pickled = std::get<QByteArray>(olmAccount.pickle(Unencrypted{}));
+    auto pickled = olmAccount.pickle(Unencrypted{}).value();
     QOlmAccount olmAccount2(QStringLiteral("@foo:bar.com"), QStringLiteral("QuotientTestDevice"));
     olmAccount2.unpickle(pickled, Unencrypted{});
     auto identityKeys2 = olmAccount2.identityKeys();
@@ -57,8 +57,7 @@ void TestOlmAccount::signatureValid()
     const auto identityKeys = olmAccount.identityKeys();
     const auto ed25519Key = identityKeys.ed25519;
     const auto verify = utility.ed25519Verify(ed25519Key, message, signature);
-    QVERIFY(std::holds_alternative<bool>(verify));
-    QVERIFY(std::get<bool>(verify) == true);
+    QVERIFY(verify.value_or(false));
 }
 
 void TestOlmAccount::oneTimeKeysValid()