When an hook is defined, a side effect was the creation of the
${notmuchIni.database.path}/.notmuch/ directory by home-manager. If
the Xapian database does not exist yet but this .notmuch directory
exists, Notmuch is confused and throws an error when `notmuch new` is
run (while this should create the database the first time).
This commit changes the hooks paths to $XDG_CONFIG_HOME where Notmuch
expects them (see notmuch-config(1)) instead of inside the maildir
database directory.
It also moves the configuration where Notmuch expects it, but the
$NOTMUCH_CONFIG environment variable is kept for backward
compatibility.
Before, loading a module would be guarded by an optional platform
condition. This made it possible to avoid loading and evaluating a
module if it did not support the host platform.
Unfortunately, this made it impossible to share a single configuration
between GNU/Linux and Darwin hosts, which some wish to do.
This removes the conditional load and instead inserts host platform
assertions in the modules that are platform specific.
Fixes#1906
I also made some modifications to the systemd service to match the [AUR version](https://aur.archlinux.org/cgit/aur.git/tree/goimapnotify@.service?h=goimapnotify) of `goimapnotify`. In particular, restarting is useful in case a network failure causes `imapnotify` to exit - that shouldn't mean that it stops trying when the network comes back up.
