Merge fort-nix/nix-bitcoin#416: secure-node: stop pruning liquidd

bac8518e7c secure-node: stop pruning liquidd (Jonas Nick)
347a0f3aee secure-node: add dummy option to determine if the preset is enabled (Jonas Nick)

Pull request description:

ACKs for top commit:
  erikarvstedt:
    ACK bac8518e7c

Tree-SHA512: df09889933355e97ccfa0cbbe3e5776e6984c492d52dd51e97220e7efbac0248599ee1187773d0db4f314b47def7cb6c5cd1074ec92cd4cfa824c8f1ee11d547

examples/configuration.nix

@@ -259,5 +259,5 @@
   # The nix-bitcoin release version that your config is compatible with.
   # When upgrading to a backwards-incompatible release, nix-bitcoin will display an
   # an error and provide hints for migrating your config to the new release.
-  nix-bitcoin.configVersion = "0.0.53";
+  nix-bitcoin.configVersion = "0.0.57";
 }

modules/presets/secure-node.nix

@@ -12,6 +12,11 @@ in {
     ./enable-tor.nix
   ];
 
+  options = {
+    # Used by ../versioning.nix
+    nix-bitcoin.secure-node-preset-enabled = {};
+  };
+
   config =  {
     # For backwards compatibility only
     nix-bitcoin.secretsDir = mkDefault "/secrets";
@@ -39,7 +44,9 @@ in {
     };
 
     services.liquidd = {
-      prune = 1000;
+      # Enable `validatepegin` to verify that a transaction sending BTC into
+      # Liquid exists on Bitcoin. Without it, a malicious liquid federation can
+      # make the node accept a sidechain that is not fully backed.
       validatepegin = true;
       listen = true;
     };

modules/versioning.nix

@@ -169,6 +169,20 @@ let
             This includes the final database size (0.4) plus some extra storage (0.2).
       '';
     }
+    {
+      version = "0.0.57";
+      condition = config.nix-bitcoin ? secure-node-preset-enabled && config.services.liquidd.enable;
+      message = ''
+        The `secure-node.nix` preset does _not_ set `liquidd.prune = 1000` anymore.
+
+          - If you want to keep the same behavior as before, manually set
+            `services.liquidd.prune = 1000;` in your configuration.nix.
+          - Otherwise, if you want to turn off pruning, you must instruct liquidd
+            to reindex by setting `services.liquidd.extraConfig = "reindex=1";`.
+            This can be removed after having started liquidd with that option
+            once.
+      '';
+    }
   ];
 
   mkOnionServiceChange = service: {