[Feature] Incorporate MCP Endpoint security with Fluxnova authorized

### Description of Problem

Provides security to MCP endpoints (/sse and /mcp) by provoding a basic credential check, using the Fluxnova engine's identity service, which then checks the user is authorized to query the resource that the invoked tool is attempting to retrieve.

### Potential Solutions

This feature has been party developed, but dropped due to maintainers not actively pursuing this feature. If anyone is keen to resurrect and maintain, see PR https://github.com/finos/fluxnova-plugins/pull/5

Start by reviewing the referenced PR #5 and tracing the /sse and /mcp MCP endpoints. Examine how the Fluxnova engine's identity service checks credentials and authorization for the resource an invoked tool retrieves. Done means the endpoints perform the described credential and resource-authorization checks, with the relevant behavior covered by the existing project tests.

Written by the indexing model from the issue text.