Adds metadata column to entry_lines table

Adds a metadata column to the entry_lines table.

This column will store currency conversion data as JSON, allowing for future flexibility in handling different types of metadata.

migrations.py

@@ -114,3 +114,14 @@ async def m001_initial(db):
             """,
             {"id": acc_id, "name": name, "type": acc_type, "description": desc}
         )
+
+
+async def m002_add_metadata_column(db):
+    """
+    Add metadata column to entry_lines table for currency conversion data.
+    """
+    await db.execute(
+        """
+        ALTER TABLE entry_lines ADD COLUMN metadata TEXT DEFAULT '{}';
+        """
+    )