systemd: move config to /etc/copyparty.conf

[9001]

the systemd examples currently assume the config file is at /etc/copyparty/copyparty.conf , however that folder is otherwise empty and doesn't serve a purpose -- its a remnant from when it was /etc/copyparty.d/ and all *.conf files inside were automatically discovered and loaded.

some of the changes that will happen before next release:

• in the system service https://github.com/9001/copyparty/blob/hovudstraum/contrib/systemd/copyparty%40.service , PRTY_CONFIG=/etc/copyparty/copyparty.conf will change to PRTY_CONFIG=/etc/copyparty.conf

• in the user service https://github.com/9001/copyparty/blob/hovudstraum/contrib/systemd/copyparty-user.service , PRTY_CONFIG=%h/.config/copyparty/copyparty.conf will change to PRTY_CONFIG=%h/.config/copyparty.conf plus related ExecStartPre changes:

  • ExecStartPre will do a nonclobbering move from %h/.config/copyparty/copyparty.conf to the new path at %h/.config/copyparty.conf so any existing user-adjusted config will be kept, but doing a similar "auto-upgrade" in the system service would likely be counterproductive and anyways prevented by pacman or similar when it installs the new package

• https://github.com/9001/copyparty/blob/hovudstraum/contrib/systemd/copyparty.conf has already been adjusted to failsafe if accidentally overriding an existing user-adjusted config ; b854b8f#diff-2deb71fcb3832a8db27f2b4341db19344bbed457a26d1c9925000e7a65ab519b

changes that should be done by distro packagers:

• to preserve user-adjusted config for the system service, any distro packages using the systemd services as-is with the old config path /etc/copyparty/copyparty.conf should add a pre-upgrade step or similar to move it to the new location /etc/copyparty.conf