Add encrypted credentials via git-crypt.

.git-crypt/.gitattributes

@@ -0,0 +1,4 @@
+# Do not edit this file.  To specify the files to encrypt, create your own
+# .gitattributes file in the directory where your files are.
+* !filter !diff
+*.gpg binary

.gitattributes

@@ -1 +1,2 @@
 * text=auto
+creds.json filter=git-crypt diff=git-crypt merge=git-crypt

.gitignore

@@ -1,2 +1 @@
 .direnv/
-creds.json

flake.nix

@@ -12,6 +12,7 @@
         devShells.default = pkgs.mkShell {
           buildInputs = with pkgs; [
             dnscontrol
+            git-crypt
           ];
         };
       }