Add deprecated discovery route (#524)

Add deprecated discovery route

Previously, we decided not to implement any routes that are deprecated
in the specification. However, as it turns out, for compatibility with
the [basyx-aas-web-ui], the `/lookup/shells` route is required.

This implements the missing route.

Fixes #522

[basyx-aas-web-ui]: https://github.com/eclipse-basyx/basyx-aas-web-ui/

---------

Co-authored-by: s-heppner <iat@s-heppner.com>

Author: Ornella33

sdk/test/model/test_string_constraints.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2025 the Eclipse BaSyx Authors
+# Copyright (c) 2026 the Eclipse BaSyx Authors
 #
 # This program and the accompanying materials are made available under the terms of the MIT License, available in
 # the LICENSE file of this project.

server/app/interfaces/discovery.py

@@ -15,7 +15,7 @@
 from app import model as server_model
 from app.adapter import jsonization
 from app.interfaces.base import BaseWSGIApp, HTTPApiDecoder
-from app.util.converters import IdentifierToBase64URLConverter
+from app.util.converters import IdentifierToBase64URLConverter, base64url_decode
 
 
 class DiscoveryStore:
@@ -98,6 +98,10 @@ def __init__(self, persistent_store: DiscoveryStore, base_path: str = "/api/v3.1
                         Submount(
                             "/lookup/shells",
                             [
+                                # Todo: This route is deprecated in the specification, but needed for interoperability
+                                #  with the BaSyx UI https://github.com/eclipse-basyx/basyx-aas-web-ui.
+                                #  Once this route is no longer needed, we should consider removing it.
+                                Rule("/", methods=["GET"], endpoint=self.get_all_aas_ids_by_asset_link),
                                 Rule(
                                     "/<base64url:aas_id>",
                                     methods=["GET"],
@@ -118,6 +122,37 @@ def __init__(self, persistent_store: DiscoveryStore, base_path: str = "/api/v3.1
             strict_slashes=False,
         )
 
+    def get_all_aas_ids_by_asset_link(
+            self, request: Request, url_args: dict, response_t: type, **_kwargs
+    ) -> Response:
+        asset_ids_param = request.args.get("assetIds", "")
+        if not asset_ids_param:
+            raise werkzeug.exceptions.BadRequest("Missing query parameter 'assetIds'")
+
+        try:
+            decoded_str = base64url_decode(asset_ids_param)
+            payload = json.loads(decoded_str)
+        except (ValueError, json.JSONDecodeError) as exc:
+            raise werkzeug.exceptions.BadRequest(f"Invalid query parameter 'assetIds': {exc}") from exc
+
+        if isinstance(payload, dict):
+            payload = [payload]
+
+        if not isinstance(payload, list):
+            raise werkzeug.exceptions.BadRequest("Decoded assetIds payload must be a JSON object or list")
+
+        matching_aas_keys = set()
+        for item in payload:
+            if not isinstance(item, dict):
+                raise werkzeug.exceptions.BadRequest("Each asset link must be a JSON object")
+
+            asset_link = server_model.AssetLink(item["name"], item["value"])
+            aas_keys = self.persistent_store.search_aas_ids_by_asset_link(asset_link)
+            matching_aas_keys.update(aas_keys)
+
+        paginated_slice, cursor = self._get_slice(request, list(matching_aas_keys))
+        return response_t(list(paginated_slice), cursor=cursor)
+
     def search_all_aas_ids_by_asset_link(
         self, request: Request, url_args: dict, response_t: type, **_kwargs
     ) -> Response: