Add 'latest-successful-db-update' info to health router

[andersy005]

Cc @katamartin

https://offsets-db-staging.fly.dev/health/

{
  "status": "ok",
  "staging": true,
  "latest-successful-db-update": {
    "clips": {
      "date": "Wed, Jan 10 2024 01:32:53 UTC",
      "url": "s3://carbonplan-offsets-db/final/2023-12-04/weekly-summary-clips.parquet"
    },
    "projects": {
      "date": "Wed, Jan 10 2024 01:32:53 UTC",
      "url": "s3://carbonplan-share/offsets-db-testing-data/final/projects-augmented.parquet"
    },
    "credits": {
      "date": "Wed, Jan 10 2024 01:32:53 UTC",
      "url": "s3://carbonplan-share/offsets-db-testing-data/final/credits-augmented.parquet"
    }
  }
}

https://offsets-db.fly.dev/health/

{
  "status": "ok",
  "staging": false,
  "latest-successful-db-update": {
    "projects": {
      "date": "Wed, Jan 10 2024 01:43:01 UTC",
      "url": "s3://carbonplan-offsets-db/final/2024-01-10/projects-augmented.parquet"
    },
    "clips": {
      "date": "Wed, Jan 10 2024 01:20:38 UTC",
      "url": "s3://carbonplan-offsets-db/final/2023-12-11/weekly-summary-clips.parquet"
    },
    "credits": {
      "date": "Wed, Jan 10 2024 01:20:38 UTC",
      "url": "s3://carbonplan-offsets-db/final/2024-01-10/credits-augmented.parquet"
    }
  }
}