The Read() method is not required to fill the whole buffer.  By
returning as soon as at least one byte was read, we allow faster
cancellation.

If seeking fails, don't leave the class with a wrong offset.

Use "size" instead.

cdio_get_devices_with_cap() can return nullptr if no drive was found,
or it can instead return an empty list.  The latter caused MPD to
crash.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

SonarLint reports the latter to be better:

std::scoped_lock basically provides the same feature as std::lock_guard,
but is more generic: It can lock several mutexes at the same time, with a
deadlock prevention mechanism (see {rule:cpp:S5524}). The equivalent code
to perform simultaneous locking with std::lock_guard is significantly more
complex. Therefore, it is simpler to use std::scoped_lock all the time,
even when locking only one mutex (there will be no performance impact).
Signed-off-by: Rosen Penev <rosenp@gmail.com>

This plugin has been defunct for several years.  Tidal has not ever
replied to any of my emails, so they're apparently not interested in
MPD support.

Found with cppcoreguidelines-special-member-functions
Signed-off-by: Rosen Penev <rosenp@gmail.com>

With the default value CURLAUTH_ANY, libcurl needs to probe for
authentication methods first, and only the second request will have an
Authorization header.

Closes https://github.com/MusicPlayerDaemon/MPD/issues/1155

Shorter.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Add cacert option for curl plugin

    add cacert option for Curl plugin. Allows to set cacert for curl lib
    Added documentation line into doc/plugins.rst with explanation for cacert option

I havn't yet figured out how to use Android's system CA certificates
with CURL/OpenSSL, so a temporary workaround is to disable verify_peer
by default.  The data MPD transfers isn't extremely important, so the
servers's authenticity isn't extremely important either.

Shorter.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

My concept with `class CancellableOperation` doesn't work properly,
because the kernel may continue to write to the given buffer as soon
as the read finishes.

To fix this, this commit adds `class ReadOperation` which owns the
buffer and the `struct iovec`.  Instances of this class persist until
the read really finishes, even if the operation is canceled.

Same as e10b867f but it got lost in
the merge, because the v0.22 branch uses a different way to detect
supported protocols at runtime.