anki: rename sync.passwordFile, improve documentation

The account password is different from the sync key needed here. Add
instructions for how to get the sync key, and make the option name
accurate.

modules/programs/anki/default.nix

@@ -17,6 +17,13 @@ in
 {
   meta.maintainers = [ lib.maintainers.junestepp ];
 
+  imports = [
+    (lib.mkRenamedOptionModule
+      [ "programs" "anki" "sync" "passwordFile" ]
+      [ "programs" "anki" "sync" "keyFile" ]
+    )
+  ];
+
   options.programs.anki = {
     enable = lib.mkEnableOption "Anki";
 
@@ -208,10 +215,23 @@ in
         description = "Path to a file containing the sync account username.";
       };
 
-      passwordFile = lib.mkOption {
+      keyFile = lib.mkOption {
         type = with lib.types; nullOr path;
         default = null;
-        description = "Path to a file containing the sync account password.";
+        description = ''
+          Path to a file containing the sync account sync key. This is different from
+          the account password.
+
+          To get the sync key, follow these steps:
+
+          - Enable this Home Manager module: `programs.anki.enable = true`
+          - Open Anki.
+          - Navigate to the sync settings page. (Tools > Preferences > Syncing)
+          - Log in to your AnkiWeb account.
+          - Select "Yes" to the prompt about saving preferences and syncing.
+          - A Home Manager warning prompt will show. Select "Show details...".
+          - Get your sync key from the message: "syncKey changed from \`None\` to \`<YOUR SYNC KEY WILL BE HERE>\`"
+        '';
       };
 
       url = lib.mkOption {

modules/programs/anki/helper.nix

@@ -164,7 +164,7 @@ in
         if cfg.sync.usernameFile == null then "None" else "Path('${cfg.sync.usernameFile}')"
       }
       key_file: Path | None = ${
-        if cfg.sync.passwordFile == null then "None" else "Path('${cfg.sync.passwordFile}')"
+        if cfg.sync.keyFile == null then "None" else "Path('${cfg.sync.keyFile}')"
       }
       custom_sync_url: str | None = ${if cfg.sync.url == null then "None" else "'${cfg.sync.url}'"}
 

tests/modules/programs/anki/full-config.nix

@@ -1,7 +1,7 @@
 { pkgs, ... }:
 let
   # This would normally not be a file in the store for security reasons.
-  testPasswordFile = pkgs.writeText "test-password-file" "password";
+  testKeyFile = pkgs.writeText "test-key-file" "a-sync-key";
 in
 {
   programs.anki = {
@@ -37,7 +37,7 @@ in
       networkTimeout = 60;
       url = "http://example.com/anki-sync/";
       username = "lovelearning@email.com";
-      passwordFile = testPasswordFile;
+      keyFile = testKeyFile;
     };
   };