refactor hydra, convert features to refs

Signed-off-by: ahuston-0 <aliceghuston@gmail.com>

hydra/spec.json

@@ -0,0 +1,35 @@
+{
+  "enabled": 1,
+  "hidden": false,
+  "description": "system flake",
+  "nixexprinput": "nixexpr",
+  "nixexprpath": ".hydra/jobsets.nix",
+  "checkinterval": 20,
+  "schedulingshares": 100,
+  "enableemail": false,
+  "emailoverride": "",
+  "keepnr": 3,
+  "type": 0,
+  "inputs": {
+    "nixexpr": {
+      "value": "https://github.com/ahuston-0/nix-dotfiles-hydra main",
+      "type": "git",
+      "emailresponsible": false
+    },
+    "nixpkgs": {
+      "value": "https://github.com/NixOS/nixpkgs nixos-unstable-small",
+      "type": "git",
+      "emailresponsible": false
+    },
+    "pulls": {
+      "type": "githubpulls",
+      "value": "ahuston-0 nix-dotfiles-hydra",
+      "emailresponsible": false
+    },
+    "branches": {
+      "type": "github_refs",
+      "value": "ahuston-0 nix-dotfiles-hydra heads -",
+      "emailresponsible": false
+    }
+  }
+}