Fix #2755: Add support for custom knowledge storage with pre-existing embeddings

Co-Authored-By: Joe Moura <joao@crewai.com>

src/crewai/knowledge/source/custom_storage_knowledge_source.py

@@ -0,0 +1,20 @@
+from typing import Optional
+
+from pydantic import Field
+
+from crewai.knowledge.source.base_knowledge_source import BaseKnowledgeSource
+from crewai.knowledge.storage.knowledge_storage import KnowledgeStorage
+
+
+class CustomStorageKnowledgeSource(BaseKnowledgeSource):
+    """A knowledge source that uses a pre-existing storage with embeddings."""
+
+    collection_name: Optional[str] = Field(default=None)
+
+    def validate_content(self):
+        """No content to validate as we're using pre-existing storage."""
+        pass
+
+    def add(self) -> None:
+        """No need to add content as we're using pre-existing storage."""
+        pass