examples: add importable-configuration.nix

This replaces minimal-configuration.nix.
importable-configuration.nix can be directly added to an existing
NixOS configuration. This makes it easy for users to get started quickly.

examples/deploy-container-minimal.sh

@@ -1,3 +1,33 @@
 #!/usr/bin/env bash
 
-exec "${BASH_SOURCE[0]%/*}/deploy-container.sh" --minimal-config "$@"
+if [[ ! -v NIX_BITCOIN_EXAMPLES_DIR ]]; then
+    echo "Running script in nix shell env..."
+    cd "${BASH_SOURCE[0]%/*}"
+    exec nix-shell --run "./${BASH_SOURCE[0]##*/} $*"
+else
+    cd "$NIX_BITCOIN_EXAMPLES_DIR"
+fi
+
+tmpDir=$(mktemp -d /tmp/nix-bitcoin-minimal-container.XXX)
+trap "rm -rf $tmpDir" EXIT
+
+# Modify importable-configuration.nix to use the local <nix-bitcoin>
+# source instead of fetchTarball
+<importable-configuration.nix sed '
+  s|nix-bitcoin = .*|nix-bitcoin = toString <nix-bitcoin>;|;
+  s|system.extraDependencies = .*||
+' > $tmpDir/importable-configuration.nix
+
+cat > $tmpDir/configuration.nix <<EOF
+  {
+    imports = [ $tmpDir/importable-configuration.nix ];
+    users.users.main = {
+      isNormalUser = true;
+      password = "a";
+    };
+    # When WAN is disabled, DNS bootstrapping slows down service startup by ~15 s
+    services.clightning.extraConfig = "disable-dns";
+  }
+EOF
+
+"${BASH_SOURCE[0]%/*}/deploy-container.sh" $tmpDir/configuration.nix "$@"