feat: add readiness contract

contracts/v1/readiness.json

@@ -0,0 +1,11 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://trixie.reaperofveriod.nl/contracts/v1/readiness.json",
+  "title": "Trixie readiness response",
+  "type": "object",
+  "additionalProperties": false,
+  "required": ["status"],
+  "properties": {
+    "status": { "enum": ["ready", "database_unavailable"] }
+  }
+}

fixtures/v1/readiness.ready.json

@@ -0,0 +1,3 @@
+{
+  "status": "ready"
+}