feat(legacy): invalidate cached assets using md5sum (#2161)

* feat(legacy): invalidate cached assets  using md5sum

Don't rely on version to invalidate cached assets

* use Assets::url() when loading legacy pages

* fix script docs

legacy/tools/assets-checksum-update.py

@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+
+# Extract the checksum for all the assets in the public directory.
+import hashlib
+import json
+from pathlib import Path
+
+legacy_root = Path(__file__).parent.parent
+
+scan_dir = legacy_root / "public"
+dest_file = legacy_root / "application/assets.json"
+result = {}
+
+
+def compute_md5(filepath: Path) -> str:
+    with filepath.open("rb") as file:
+        buffer = hashlib.md5()  # nosec
+        while True:
+            blob = file.read(8192)
+            if not blob:
+                break
+            buffer.update(blob)
+
+        return buffer.hexdigest()
+
+
+def compute_md5_foreach_asset_in(root: Path):
+    for path in root.iterdir():
+        if path.is_dir():
+            compute_md5_foreach_asset_in(path)
+        else:
+            if path.suffix in (".js", ".css"):
+                result_key = str(path)[len(str(scan_dir)) + 1 :]
+                result[result_key] = compute_md5(path)
+
+
+compute_md5_foreach_asset_in(scan_dir)
+dest_file.write_text(json.dumps(dict(sorted(result.items())), indent=2) + "\n")