Add support for integrating into nix/nixos

modules/microsite/docs/dev.md

@@ -80,6 +80,46 @@ docspell.joex {
 }
 ```
 
+## Nix Expressions
+
+The directory `/nix` contains nix expressions to install docspell via
+the nix package manager and to integrate it into NixOS.
+
+### Testing NixOS Modules
+
+The modules can be build by building the `configuration-test.nix` file
+together with some nixpkgs version. For example:
+
+``` shell
+nixos-rebuild build-vm -I nixos-config=./configuration-test.nix \
+  -I nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-19.09.tar.gz
+```
+
+This will build all modules imported in `configuration-test.nix` and
+create a virtual machine containing the system. After that completes,
+the system configuration can be found behind the `./result/system`
+symlink. So it is possible to look at the generated systemd config for
+example:
+
+``` shell
+cat result/system/etc/systemd/system/docspell-joex.service
+```
+
+And with some more commands (there probably is an easier way…) the
+config file can be checked:
+
+``` shell
+cat result/system/etc/systemd/system/docspell-joex.service | grep ExecStart | cut -d'=' -f2 | xargs cat | tail -n1 | awk '{print $NF}'| sed 's/.$//' | xargs cat | jq
+```
+
+To see the module in action, the vm can be started (the first line
+sets more memory for the vm):
+
+``` shell
+export QEMU_OPTS="-m 2048"
+./result/bin/run-docspelltest-vm
+```
+
 ## ADRs
 
 Some early information about certain details can be found in the few

modules/restserver/src/main/resources/reference.conf

@@ -23,7 +23,7 @@ docspell.server {
     # The secret for this server that is used to sign the authenicator
     # tokens. If multiple servers are running, all must share the same
     # secret. You can use base64 or hex strings (prefix with b64: and
-    # hex:, respectively)
+    # hex:, respectively).
     server-secret = "hex:caffee"
 
     # How long an authentication token is valid. The web application
@@ -68,9 +68,10 @@ docspell.server {
     }
 
     files {
-      # Defines the chunk size used to store bytes. This will affect
-      # the memory footprint when uploading and downloading files. At
-      # most this amount is loaded into RAM for down- and uploading.
+      # Defines the chunk size (in bytes) used to store the files.
+      # This will affect the memory footprint when uploading and
+      # downloading files. At most this amount is loaded into RAM for
+      # down- and uploading.
       #
       # It also defines the chunk size used for the blobs inside the
       # database.