Implement attaching files to vector stores

This adds the ability to attach files to vector
stores (client.vector_stores.files.create) for the OpenAI Vector
Stores Files API.

The initial implementation is only for Faiss, and tested via the
existing test_responses.py::test_response_non_streaming_file_search.

Signed-off-by: Ben Browning <bbrownin@redhat.com>

docs/_static/llama-stack-spec.yaml

@@ -2263,6 +2263,43 @@ paths:
             schema:
               $ref: '#/components/schemas/LogEventRequest'
         required: true
+  /v1/openai/v1/vector_stores/{vector_store_id}/files:
+    post:
+      responses:
+        '200':
+          description: >-
+            A VectorStoreFileObject representing the attached file.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/VectorStoreFileObject'
+        '400':
+          $ref: '#/components/responses/BadRequest400'
+        '429':
+          $ref: >-
+            #/components/responses/TooManyRequests429
+        '500':
+          $ref: >-
+            #/components/responses/InternalServerError500
+        default:
+          $ref: '#/components/responses/DefaultError'
+      tags:
+        - VectorIO
+      description: Attach a file to a vector store.
+      parameters:
+        - name: vector_store_id
+          in: path
+          description: >-
+            The ID of the vector store to attach the file to.
+          required: true
+          schema:
+            type: string
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/OpenaiAttachFileToVectorStoreRequest'
+        required: true
   /v1/openai/v1/completions:
     post:
       responses:
@@ -8289,6 +8326,148 @@ components:
         - event
         - ttl_seconds
       title: LogEventRequest
+    VectorStoreChunkingStrategy:
+      oneOf:
+        - $ref: '#/components/schemas/VectorStoreChunkingStrategyAuto'
+        - $ref: '#/components/schemas/VectorStoreChunkingStrategyStatic'
+      discriminator:
+        propertyName: type
+        mapping:
+          auto: '#/components/schemas/VectorStoreChunkingStrategyAuto'
+          static: '#/components/schemas/VectorStoreChunkingStrategyStatic'
+    VectorStoreChunkingStrategyAuto:
+      type: object
+      properties:
+        type:
+          type: string
+          const: auto
+          default: auto
+      additionalProperties: false
+      required:
+        - type
+      title: VectorStoreChunkingStrategyAuto
+    VectorStoreChunkingStrategyStatic:
+      type: object
+      properties:
+        type:
+          type: string
+          const: static
+          default: static
+        static:
+          $ref: '#/components/schemas/VectorStoreChunkingStrategyStaticConfig'
+      additionalProperties: false
+      required:
+        - type
+        - static
+      title: VectorStoreChunkingStrategyStatic
+    VectorStoreChunkingStrategyStaticConfig:
+      type: object
+      properties:
+        chunk_overlap_tokens:
+          type: integer
+          default: 400
+        max_chunk_size_tokens:
+          type: integer
+          default: 800
+      additionalProperties: false
+      required:
+        - chunk_overlap_tokens
+        - max_chunk_size_tokens
+      title: VectorStoreChunkingStrategyStaticConfig
+    OpenaiAttachFileToVectorStoreRequest:
+      type: object
+      properties:
+        file_id:
+          type: string
+          description: >-
+            The ID of the file to attach to the vector store.
+        attributes:
+          type: object
+          additionalProperties:
+            oneOf:
+              - type: 'null'
+              - type: boolean
+              - type: number
+              - type: string
+              - type: array
+              - type: object
+          description: >-
+            The key-value attributes stored with the file, which can be used for filtering.
+        chunking_strategy:
+          $ref: '#/components/schemas/VectorStoreChunkingStrategy'
+          description: >-
+            The chunking strategy to use for the file.
+      additionalProperties: false
+      required:
+        - file_id
+      title: OpenaiAttachFileToVectorStoreRequest
+    VectorStoreFileLastError:
+      type: object
+      properties:
+        code:
+          oneOf:
+            - type: string
+              const: server_error
+            - type: string
+              const: rate_limit_exceeded
+        message:
+          type: string
+      additionalProperties: false
+      required:
+        - code
+        - message
+      title: VectorStoreFileLastError
+    VectorStoreFileObject:
+      type: object
+      properties:
+        id:
+          type: string
+        object:
+          type: string
+          default: vector_store.file
+        attributes:
+          type: object
+          additionalProperties:
+            oneOf:
+              - type: 'null'
+              - type: boolean
+              - type: number
+              - type: string
+              - type: array
+              - type: object
+        chunking_strategy:
+          $ref: '#/components/schemas/VectorStoreChunkingStrategy'
+        created_at:
+          type: integer
+        last_error:
+          $ref: '#/components/schemas/VectorStoreFileLastError'
+        status:
+          oneOf:
+            - type: string
+              const: completed
+            - type: string
+              const: in_progress
+            - type: string
+              const: cancelled
+            - type: string
+              const: failed
+        usage_bytes:
+          type: integer
+          default: 0
+        vector_store_id:
+          type: string
+      additionalProperties: false
+      required:
+        - id
+        - object
+        - attributes
+        - chunking_strategy
+        - created_at
+        - status
+        - usage_bytes
+        - vector_store_id
+      title: VectorStoreFileObject
+      description: OpenAI Vector Store File object.
     OpenAIJSONSchema:
       type: object
       properties: