CloudCode (MongoDB) docs: static IPs, auth examples, and template updates

[michaelbarnes]

Summary
Updates the CloudCode for MongoDB doc to match the current template, add a full static IP setup flow, and improve production/auth sections.

Changes

• Static IP Addresses (MongoDB Atlas)
  New section that walks through:

  • Converting the MongoDB SRV record to replica connection URIs with @journeyapps/https-proxy-socket.
  • Requesting an egress token from PowerSync support (what to include: replicas URI, Oxide Project URL, and multi-deployment/region details when needed).
  • Configuring allowed IPs in MongoDB Atlas (Database & Network Access → IP Access List).
  • Updating the upload CloudCode task to use the proxy helper, including:
    • Note for the latest template (uncomment proxy snippets and set CLOUDCODE_EGRESS_TOKEN).
    • Steps for older templates: add @journeyapps/https-proxy-socket, update MongoDBStorage and closeConnection as shown.
  • A reference table of static IPs by Region (EU/US) and Group (A/B/C) for use when requesting the egress token and configuring Atlas.

• Production considerations

  • New HTTP Endpoint Authentication subsection: default behavior vs production, plus full authenticate examples using jsonwebtoken (secret) and jose (JWKS).
  • Other considerations tightened around schema validation and MongoDB Schema Validation.

• Template and wording

  • Aligned steps and code with the current CloudCode task template.
  • Consistently use “group” (instead of “zone”) for the static IP groups provided by support.
  • Minor heading and example tweaks from the refactor pass.

• Fix

  • Resolved MDX parse error caused by <uri_1,uri_2,etc.> being interpreted as JSX by escaping/wrapping in code.

[michaelbarnes]

This PR is pending a merge of the updated CloudCode CRUD & Auth template CC task. Once that's done I'll change the PR status.