fix: MCP authorization parameter implementation (#4052)

# What does this PR do?
Adding a user-facing `authorization ` parameter to MCP tool definitions
that allows users to explicitly configure credentials per MCP server,
addressing GitHub Issue #4034 in a secure manner.


## Test Plan
tests/integration/responses/test_mcp_authentication.py

---------

Co-authored-by: Omar Abdelwahab <omara@fb.com>
Co-authored-by: Ashwin Bharambe <ashwin.bharambe@gmail.com>

docs/static/llama-stack-spec.yaml

@@ -1878,6 +1878,13 @@ paths:
           required: false
           schema:
             $ref: '#/components/schemas/URL'
+        - name: authorization
+          in: query
+          description: >-
+            (Optional) OAuth access token for authenticating with the MCP server.
+          required: false
+          schema:
+            type: string
       deprecated: false
   /v1/toolgroups:
     get:
@@ -6182,6 +6189,10 @@ components:
               - type: object
           description: >-
             (Optional) HTTP headers to include when connecting to the server
+        authorization:
+          type: string
+          description: >-
+            (Optional) OAuth access token for authenticating with the MCP server
         require_approval:
           oneOf:
             - type: string
@@ -8366,6 +8377,10 @@ components:
               - type: object
           description: >-
             A dictionary of arguments to pass to the tool.
+        authorization:
+          type: string
+          description: >-
+            (Optional) OAuth access token for authenticating with the MCP server.
       additionalProperties: false
       required:
         - tool_name