Allow metadata to be passed to MCP calls

[jacquicollier2-eng]

In Spring AI it is possible to pass metadata to MCP calls, e.g.,

@McpTool(
    generateOutputSchema = true,
    description = "Fetches jobs for the current worker..."
)
public BrowseJobsToolResponse browseJobs(McpMeta meta) { ... }

can be called by setting the data in the toolContext in Spring AI. E.g.,

chatClient.prompt(prompt)
    .toolCallbacks(toolCallbacks())
    .toolContext(toolContext(Map.of("authToken", authToken())))
    .call();

It would be good to be able to send metadata in MCP calls in Embabel too.