Implement v2.x compatibility endpoints

[offa]

InfluxDB v1.8 supports v2.x forward compatibility:

https://docs.influxdata.com/influxdb/v1.8/tools/api/#influxdb-20-api-compatibility-endpoints

• Do non-http transport support this?
• Support for Auth Token? #90

[offa]

Influxdb v3.x still supports the 1.x endpoints, so I'm not sure if it still makes sense to implement the v2.x compatibility endpoint.