Replaces all string configuration options with enum types
that can be checked by the compiler. This prevents spelling
errors, in-place configuration definitions, and inconsistent
default values. The default value config getter signature was
removed in favour of consistently and centrally default-initialised
configuration values.
Individual default values were adjusted for better security,
such as the default password length, which was increased from
16 characters to 32.
The already existing config option deprecation map was extended
by a general migration procedure using configuration versioning.
Settings were split into Roaming and Local settings, which
go to their respective AppData locations on Windows.
Fixes#2574Fixes#2193
* Prefer clearing clipboard by explicitly setting the clipboard to an empty string. Qt's QClipboard::clear() method is unreliable under X11 environment.
* Fixes#4126
Performing a dev build against the latest version of Qt failed
because of some deprecated members. They have been replaced
according to the Qt documentation.
Further, Q_OS_MACOS is now the only macro available to identify a
machine running macOS, the others are now deprecated.
See https://doc.qt.io/qt-5/qtglobal.html#Q_OS_OSX and
https://doc.qt.io/qt-5/qtglobal.html#Q_OS_MAC.
