docs(neo4j): update to reflect standalone node support (#338)

Author: badmonster0

docs/docs/ops/storages.md

@@ -48,36 +48,46 @@ You can find an end-to-end example [here](https://github.com/cocoindex-io/cocoin
 
 ## Neo4j
 
-### Setup
-
 If you don't have a Postgres database, you can start a Postgres SQL database for cocoindex using our docker compose config:
 
 ```bash
 docker compose -f <(curl -L https://raw.githubusercontent.com/cocoindex-io/cocoindex/refs/heads/main/dev/neo4j.yaml) up -d
 ```
 
-### Neo4jRelationship
-
-The `Neo4jRelationship` storage exports each row as a relationship to Neo4j Knowledge Graph.
-When you collect rows for `Neo4jRelationship`, fields will be mapped to a relationship and source/target nodes for the relationship:
+:::warning
 
-*   You can explicitly specify fields mapped to source/target nodes.
-*   All remaining fields will be mapped to relationship properties by default.
+The docker compose config above will start a Neo4j Enterprise instance under the [Evaluation License](https://neo4j.com/terms/enterprise_us/),
+with 30 days trial period.
+Please read and agree the license before starting the instance.
 
+:::
 
-The spec takes the following fields:
+The `Neo4j` storage exports each row as a relationship to Neo4j Knowledge Graph. The spec takes the following fields:
 
 *   `connection` (type: [auth reference](../core/flow_def#auth-registry) to `Neo4jConnectionSpec`): The connection to the Neo4j database. `Neo4jConnectionSpec` has the following fields:
     *   `uri` (type: `str`): The URI of the Neo4j database to use as the internal storage, e.g. `bolt://localhost:7687`.
     *   `user` (type: `str`): Username for the Neo4j database.
     *   `password` (type: `str`): Password for the Neo4j database.
     *   `db` (type: `str`, optional): The name of the Neo4j database to use as the internal storage, e.g. `neo4j`.
-*   `rel_type` (type: `str`): The type of the relationship.
-*   `source`/`target` (type: `Neo4jRelationshipEndSpec`): The source/target node of the relationship, with the following fields:
-    *   `label` (type: `str`): The label of the node.
-    *   `fields` (type: `list[Neo4jFieldMapping]`): Map fields from the collector to nodes in Neo4j, with the following fields:
-        *   `field_name` (type: `str`): The name of the field in the collected row.
-        *   `node_field_name` (type: `str`, optional): The name of the field to use as the node field. If unspecified, will use the same as `field_name`.
-*   `nodes` (type: `dict[str, Neo4jRelationshipNodeSpec]`): This configures indexes for different node labels. Key is the node label. The value `Neo4jRelationshipNodeSpec` has the following fields to configure [storage indexes](../core/flow_def#storage-indexes) for the node.
-        *   `primary_key_fields` is required.
-        *   `vector_indexes` is also supported and optional.
+*   `mapping`: The mapping from collected row to nodes or relationships of the graph. 2 variations are supported:
+    *   `cocoindex.storages.GraphNode`: each collected row is mapped to a node in the graph. It has the following fields:
+        *   `label`: The label of the node.
+    *   `cocoindex.storages.GraphRelationship`: each collected row is mapped to a relationship in the graph,
+        With the following fields:
+
+        *   `rel_type` (type: `str`): The type of the relationship.
+        *   `source`/`target` (type: `cocoindex.storages.GraphRelationshipEnd`): The source/target node of the relationship, with the following fields:
+            *   `label` (type: `str`): The label of the node.
+            *   `fields` (type: `list[cocoindex.storages.GraphFieldMapping]`): Map fields from the collector to nodes in Neo4j, with the following fields:
+                *   `field_name` (type: `str`): The name of the field in the collected row.
+                *   `node_field_name` (type: `str`, optional): The name of the field to use as the node field. If unspecified, will use the same as `field_name`.
+
+            :::info
+
+            All fields specified in `fields` will be mapped to properties of source/target nodes. All remaining fields will be mapped to relationship properties by default.
+
+            :::
+
+        *   `nodes` (type: `dict[str, cocoindex.storages.GraphRelationshipNode]`): This configures indexes for different node labels. Key is the node label. The value type `GraphRelationshipNode` has the following fields to configure [storage indexes](../core/flow_def#storage-indexes) for the node.
+                *   `primary_key_fields` is required.
+                *   `vector_indexes` is also supported and optional.