When restoring a backup, discourse decompresses the backup archive in
the /share/discourse/tmp dir. Before this change, it is linked to /run
which is typically backed by memory, so the backup will fail to
restore if you do not have enough memory on your system to contain the
backup. This has already happened to me on two small forums.
This moves tmp to the StateDirectory /var/lib/discourse/tmp which is
typically backed by disk.
For plugins to work properly, their assets need to be precompiled
along with the rest of Discourse's assets. This means we need to build
new packages when the list of plugins change.
Assert that the PostgreSQL version being deployed is the one used
upstream. Allow the user to override this assertion, since it's not
always possible or preferable to use the recommended one.
Using `replace-literal` to insert secrets leaks the secrets through
the `replace-literal` process' `/proc/<pid>/cmdline`
file. `replace-secret` solves this by reading the secret straight from
the file instead, which also simplifies the code a bit.
Bash doesn't handle subshell errors properly if the result is used as
input to a command. To cause the services to fail when the files can't
be read, we need to assign the value to a variable, then export it
separately.
