I18n: extract node group asset sockets

Each node group asset exposes various properties through sockets.
Although they can generally be considered user-created data, for
built-in assets they are also part of the UI and should be
translated--especially since more modifiers should be migrated to
Geometry Nodes in the future.

This commit allows extraction of such socket names and descriptions.
Since the message extraction script already extracted names and
descriptions for each asset, this commit only adds the socket in the
same loop, so that they are extracted while the asset file is already
being read.

Properties from sockets are not yet translated in the modifier
properties editor, this will be enabled in a follow-up commit.

scripts/modules/bl_i18n_utils/bl_extract_messages.py

@@ -941,6 +941,14 @@ def dump_asset_messages(msgs, reports, settings):
 
     # Parse the asset blend files
     asset_files = {}
+    # Store assets according to this structure:
+    # {"basename": [
+    #     {"name": "Name",
+    #      "description": "Description",
+    #      "sockets": [
+    #          ("Name", "Description"),
+    #      ]},
+    # ]}
 
     bfiles = glob.glob(assets_dir + "/**/*.blend", recursive=True)
     for bfile in bfiles:
@@ -953,11 +961,18 @@ def dump_asset_messages(msgs, reports, settings):
                 if asset.asset_data is None:  # Not an asset
                     continue
                 assets = asset_files.setdefault(basename, [])
-                assets.append((asset.name, asset.asset_data.description))
+                asset_data = {"name": asset.name,
+                              "description": asset.asset_data.description}
+                for interface in asset.interface.items_tree:
+                    if interface.name == "Geometry":  # Ignore common socket
+                        continue
+                    socket_data = asset_data.setdefault("sockets", [])
+                    socket_data.append((interface.name, interface.description))
+                assets.append(asset_data)
 
     for asset_file in sorted(asset_files):
-        for asset in sorted(asset_files[asset_file]):
-            name, description = asset
+        for asset in sorted(asset_files[asset_file], key=lambda a: a["name"]):
+            name, description = asset["name"], asset["description"]
             msgsrc = "Asset name from file " + asset_file
             process_msg(msgs, settings.DEFAULT_CONTEXT, name, msgsrc,
                         reports, None, settings)
@@ -965,6 +980,15 @@ def dump_asset_messages(msgs, reports, settings):
             process_msg(msgs, settings.DEFAULT_CONTEXT, description, msgsrc,
                         reports, None, settings)
 
+            if "sockets" in asset:
+                for socket_name, socket_description in asset["sockets"]:
+                    msgsrc = f"Socket name from node group {name}, file {asset_file}"
+                    process_msg(msgs, settings.DEFAULT_CONTEXT, socket_name, msgsrc,
+                                reports, None, settings)
+                    msgsrc = f"Socket description from node group {name}, file {asset_file}"
+                    process_msg(msgs, settings.DEFAULT_CONTEXT, socket_description, msgsrc,
+                                reports, None, settings)
+
 
 def dump_addon_bl_info(msgs, reports, module, settings):
     for prop in ('name', 'location', 'description', 'warning'):