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

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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

internal/log/authorize.go

@@ -22,6 +22,9 @@ const (
 	AuthorizeLogFieldImpersonateSessionID AuthorizeLogField = "impersonate-session-id"
 	AuthorizeLogFieldImpersonateUserID    AuthorizeLogField = "impersonate-user-id"
 	AuthorizeLogFieldIP                   AuthorizeLogField = "ip"
+	AuthorizeLogFieldMCPMethod            AuthorizeLogField = "mcp-method"
+	AuthorizeLogFieldMCPTool              AuthorizeLogField = "mcp-tool"
+	AuthorizeLogFieldMCPToolParameters    AuthorizeLogField = "mcp-tool-parameters"
 	AuthorizeLogFieldMethod               AuthorizeLogField = "method"
 	AuthorizeLogFieldPath                 AuthorizeLogField = "path"
 	AuthorizeLogFieldQuery                AuthorizeLogField = "query"
@@ -72,6 +75,9 @@ var authorizeLogFieldLookup = map[AuthorizeLogField]struct{}{
 	AuthorizeLogFieldImpersonateSessionID: {},
 	AuthorizeLogFieldImpersonateUserID:    {},
 	AuthorizeLogFieldIP:                   {},
+	AuthorizeLogFieldMCPMethod:            {},
+	AuthorizeLogFieldMCPTool:              {},
+	AuthorizeLogFieldMCPToolParameters:    {},
 	AuthorizeLogFieldMethod:               {},
 	AuthorizeLogFieldPath:                 {},
 	AuthorizeLogFieldQuery:                {},