chore: cleanup and nixify

* create containers with nix
* updated README.md
* added SPDX license headers

Signed-off-by: Harald Hoyer <harald@matterlabs.dev>

packages/container-vault-unseal/default.nix

@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: Apache-2.0
+# Copyright (c) 2024 Matter Labs
+{ lib
+, dockerTools
+, nixsgx
+, teepot
+, buildEnv
+, curl
+, ...
+}:
+dockerTools.buildLayeredImage {
+  name = "vault-unseal";
+  tag = "latest";
+
+  config.Entrypoint = [ "${teepot.teepot.vault_unseal}/bin/vault-unseal" ];
+
+  contents = buildEnv {
+    name = "image-root";
+    paths = with dockerTools; with nixsgx;[
+      azure-dcap-client
+      curl
+      sgx-dcap.quote_verify
+      usrBinEnv
+      binSh
+      caCertificates
+      fakeNss
+      teepot.teepot.vault_unseal
+    ];
+    pathsToLink = [ "/bin" "/lib" "/etc" ];
+  };
+}