Restore all docs to version-4 branch

[glasser]

trafficstars

We removed all the docs on version-4 because they had not been evaluated to see if they are up to date. We need to restore all of them and make sure they are accurate.

Pages to Update

• [x] Introduction
• [x] Get started
• [ ] Choosing which package to use New in v3
  • [x] Migrating to Apollo Server 3 Defining a Schema
  • [x] Schema basics
  • [x] Unions and interfaces
  • [x] Custom scalars
  • [x] Directives
  • [x] Creating directives (REMOVED) Fetching Data
  • [x] Resolvers
  • [x] Data sources (REPLACED "Fetching from REST")
  • [x] Error handling
  • [x] File uploads (REMOVED)
  • [x] Subscriptions Development Workflow
  • [x] Build and run queries
  • [x] Request format
  • [x] Mocking
  • [x] Integration testing Performance
  • [x] Caching
  • [x] Cache backends
  • [x] Automatic persisted queries Security
  • [x] Auth
  • [x] CORS
  • [x] Terminating SSL
  • [x] Proxy configuration Deployment
  • [x] Heroku
  • [ ] Lambda
  • [ ] Azure Functions
  • [ ] Google Cloud Functions Monitoring
  • [x] Metrics and logging
  • [x] Health checks API Reference
  • [x] ApolloServer Built-in Plugins
  • [x] Overview
  • [x] Usage reporting
  • [x] Schema reporting
  • [x] Inline trace
  • [x] Drain HTTP server
  • [x] Cache control
  • [x] Landing pages Custom Plugins
  • [x] Creating plugins
  • [x] Event reference

[glasser]

(Assigning @rkoron007 but this is likely a group project.)

[rkoron007]

Added the checklist of pages to update! :)

[rkoron007]

Things left to do:

• handle the deployment articles for the different AS4 integrations (once they exist)
• Figure how we want to handle the "Choosing which package to use" article.
  • It does feel like an article covering the different integrations would be a great add

[glasser]

I'm very excited to mark this as complete!