HTTP Output Compression

[madisonleavo]

Feature Request

Enable HTTP Compression for outgoing HTTP

Proposal:

Enable HTTP Compression for outgoing HTTP. Really only makes sense for POST with batched data.
Could be set similar to influxdb OUTPUT config (though 'identity' doesn't make sense in straight HTTP context). Might even be able to copy/paste code to implement from influxdb plugin.

## HTTP Content-Encoding for write request body, can be set to "gzip" to
## compress body or "identity" to apply no encoding.
  # content_encoding = "identity"

Current behavior:

Uncompressed body is the only option.

Desired behavior:

1. Enable Compression (gzip, deflate, br, etc) through telegraf.conf
2. Set correct Content-Encoding HTTP header to match chosen compression.
3. Compress payload

Use case: [Why is this important (helps with prioritizing requests)]

We use Telegraf as sidecar for docker containers on machines that have terrible bandwidth. Every byte saved helps.