nixos/nextcloud: fix nginx routing to store and nix apps

Closes #277206

The bug mentioned above was a symptom of the issue fixed here: when
opening the `forms` app which is installed via `extraApps` (or the
app store) the site wouldn't work because `.mjs` files had the wrong
Content-Type.

The actual problem got fixed already[1], however this config was not
used for stuff from `/nix-apps` & `/store-apps` which had their own
location section with only a `root ;` statement.

In fact, this setup isn't strictly supported by Nextcloud upstream[2],
so to fix this for good, I decided to follow the upstream suggestion for
app directories outside the server root, i.e. linking them back into the
store path.

This means that the module generates a new derivation now with

* `services.nextcloud.package` linked into it via `lndir`.
* under `nix-apps` is a symlink to the link farm containing all apps
  from `services.nextcloud.extraApps`.
* under `store-apps` is a symlink to `/var/lib/nextcloud/store-apps`.
  Since this is only used in the NixOS module that also configures this
  location for imperatively installed apps, this seems an OK thing to
  do.

Successfully tested the change on a productive Nextcloud 28.0.1 with
several apps installed via `extraApps` (`forms`, `cospend`, `maps`,
`user_saml` and a few more).

[1] 292c74c7a92efe45cfdfc091fb48d8c575346a95
[2] https://docs.nextcloud.com/server/28/admin_manual/apps_management.html#using-custom-app-directories

0 files changed, 0 insertions, 0 deletions