bootstrap: planned object-storage reef, no rail

Declare reef-storage as substrate_kind object-storage. Hold non-secret
attribute paths for Scaleway S3. Do not host a compute rail.

schemas/object-store-attributes.schema.json

@@ -0,0 +1,22 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://railiance.dev/reef-storage/object-store-attributes.schema.json",
+  "title": "Non-secret object-store attributes",
+  "type": "object",
+  "additionalProperties": false,
+  "required": ["schema_version", "resource_id", "provider", "status"],
+  "properties": {
+    "schema_version": {"const": "0.1"},
+    "resource_id": {"type": "string", "pattern": "^resource:"},
+    "provider": {"type": "string", "minLength": 1},
+    "status": {"enum": ["planned", "active", "retired"]},
+    "endpoint": {"type": ["string", "null"]},
+    "region": {"type": ["string", "null"]},
+    "bucket": {"type": ["string", "null"]},
+    "prefix": {"type": ["string", "null"]},
+    "versioning": {"type": ["boolean", "null"]},
+    "lifecycle": {"type": ["string", "null"]},
+    "provider_project_ref": {"type": ["string", "null"]},
+    "notes": {"type": "array", "items": {"type": "string"}}
+  }
+}