Problem:
- Many constructors are defined as `{}` rather than using the ` =
default` compiler-provided constructor.
- Some types provide an implicit conversion operator from `nullptr_t`
instead of requiring the caller to default construct. This violates
the C++ Core Guidelines suggestion to declare single-argument
constructors explicit
(https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c46-by-default-declare-single-argument-constructors-explicit).
Solution:
- Change default constructors to use the compiler-provided default
constructor.
- Remove implicit conversion operators from `nullptr_t` and change
usage to enforce type consistency without conversion.
Clients of LaunchServer can now provide a list of allowed handlers,
optionally with a specific set of URLs. The list can be sealed to
prevent future additions to it.
If LaunchServer receives a request to open something not on the allowed
handlers list, it will disconnect the client immediately.
The main idea here is to allow otherwise restricted programs to launch
specific things, e.g "Help" to open their manual, or "Browser" to load
the SerenityOS home page. :^)
This patch introduces IPC::Connection which becomes the new base class
of ClientConnection and ServerConnection. Most of the functionality
has been hoisted up to the base class since almost all of it is useful
on both sides.
This gives us the ability to send synchronous messages in both
directions, which is needed for the WebContent server process.
Unlike other servers, WebContent does not mind blocking on a response
from its client.
Adds metadata about apps for what file types and protocols they can
handle, then consumes that in the LaunchServer. The LaunchServer can
then use that to offer multiple options for what apps can open a given
URL. Callers can then pass back the handler name to the LaunchServer to
use an alternate app :)
Step one of moving DesktopServices::open handling out of process. This
makes it easier to do things like read in associations for which program
opens which files or protocols. This gives users the ability to modify
the associations without having to rebuild :^)
