feat(ops/secrets): Use korora for type checking secrets

Type checking of secrets was removed in cff6575948 to get rid of yants.
This adds back type checking using Korora.

Fixes https://git.snix.dev/snix/snix/issues/71
Change-Id: I27cd47b7e1810be5c4cd5d86366e860ca217f9c4
Reviewed-on: https://cl.snix.dev/c/snix/+/30118
Tested-by: besadii
Reviewed-by: Ryan Lahfa <masterancpp@gmail.com>
Reviewed-by: Florian Klink <flokli@flokli.de>

third_party/sources/sources.json

@@ -48,6 +48,18 @@
         "url": "https://github.com/hercules-ci/gitignore.nix/archive/637db329424fd7e46cf4185293b9cc8c88c95394.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
+    "korora": {
+        "branch": "master",
+        "description": "A tiny & fast type system for Nix in Nix",
+        "homepage": "",
+        "owner": "adisbladis",
+        "repo": "korora",
+        "rev": "f7d8f17c4f20b69bc77189d4202c59c680400623",
+        "sha256": "15im7sm7z36n128g38fz3dcy26qml7vzj986x0nfpzwgyd7499pb",
+        "type": "tarball",
+        "url": "https://github.com/adisbladis/korora/archive/f7d8f17c4f20b69bc77189d4202c59c680400623.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
     "naersk": {
         "branch": "master",
         "description": "Build rust crates in Nix. No configuration, no code generation, no IFD. Sandbox friendly. [maintainer: @Patryk27]",