mcp: add mcp method and tool logging to authorize (#5668)

## Summary

Adds support for extending authorization log with Model Context Protocol
details.

i.e. 
```json
{
  "level": "info",
  "server-name": "all",
  "service": "authorize",
  "mcp-method": "tools/call",
  "mcp-tool": "describe_table",
  "mcp-tool-parameters": { "table_name": "Categories" },
  "allow": true,
  "allow-why-true": ["email-ok", "mcp-tool-ok"],
  "deny": false,
  "deny-why-false": [],
  "time": "2025-06-24T17:40:41-04:00",
  "message": "authorize check"
}
```

## Related issues

Fixes
https://linear.app/pomerium/issue/ENG-2393/mcp-authorize-each-incoming-request-to-an-mcp-route

## User Explanation

<!-- How would you explain this change to the user? If this
change doesn't create any user-facing changes, you can leave
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## Checklist

- [x] reference any related issues
- [x] updated unit tests
- [x] add appropriate label (`enhancement`, `bug`, `breaking`,
`dependencies`, `ci`)
- [x] ready for review

pkg/policy/criteria/mcp_tool.go

@@ -32,7 +32,7 @@ func (c mcpToolCriterion) GenerateRule(_ string, data parser.Value) (*ast.Rule,
 			ast.MustParseExpr(`input.mcp.method == "tools/call"`),
 		},
 	}
-	toolRef := ast.RefTerm(ast.VarTerm("input"), ast.VarTerm("mcp"), ast.VarTerm("tool"))
+	toolRef := ast.RefTerm(ast.VarTerm("input"), ast.VarTerm("mcp"), ast.VarTerm("tool_call"), ast.VarTerm("name"))
 	err := matchString(&r2.Body, toolRef, data)
 	if err != nil {
 		return nil, nil, err