Connecting OSS to Cloud

[timhallinflux]

We need to describe the various ways that OSS and Cloud can be used together. This should include:

1. Monitoring InfluxDB with InfluxDB Cloud Free Tier (Addresses: Add documentation for monitoring your InfluxDB OSS instance #2567)
   a. InfluxDB 1.x OSS -- within https://docs.influxdata.com/platform/monitoring/influxdata-platform/
   1) Self-service with Template
   b. InfluxDB 1.x Enterprise -- within https://docs.influxdata.com/platform/monitoring/influxdata-platform/
   1) Self-service with Template
   2) Co-monitoring with InfluxData support via Insights (work with @veereshhosakere on this content)
   c. InfluxDB 2.x OSS
   1) Self-service with Template -- leverage: https://www.influxdata.com/blog/monitor-your-influxdb-open-source-instances-with-influxdb-cloud/

2. Writing Data to OSS and Cloud (aka Dual Write scenario)
   a. Describe Telegraf setup for dual write within https://docs.influxdata.com/influxdb/v2.0/write-data/no-code/use-telegraf/ (This content applies to both Cloud and OSS....can be used in both places).

3. Selective writing of Data to Cloud (OSS content)
   a. Using Flux to --- make sure to provide caveats similar to those contained within this blog https://www.influxdata.com/blog/how-to-consolidate-oss-data-into-cloud-account/ (the blog outlines a very selective construction of line protocol and leverages HTTP POST). Flux with the to enhancements will allow for more data to be transmitted with less code. However, the limitations around rate limits, volume, retries, etc. will all still apply.

@russorat to add more scenarios.

[kelseiv]

splitting this issue for visibility:
#1 has been completed
#2 assigned to @noramullen1 #3321
#3 assigned to @sanderson #3322