Basepath not used for generated telegraf url

[mapero]

Steps to reproduce:

1. Compile influxdb with custom basepath "/influxdb"
2. Set reverse proxy configuration accordingly so that the application is running under https://10.52.126.234/influxdb
3. Use "Load Data" -> "Telegraf" -> "Create Configuration"
4. Select "Bucket" and "System", and give it a name
5. Urls generated for telegraf are not respecting basepath

Expected behavior:

I expect, that the generated urls to download the configuration and the url field in configuration respect the "basepath" parameter.
e.g.

telegraf --config https://10.52.126.234/influxdb/api/v2/telegrafs/1234567878

[[outputs.influxdb_v2]]
urls = ["https://10.52.126.234/influxdb"]

Actual behavior:

Generated urls ignore basepath configuration

telegraf --config https://10.52.126.234/api/v2/telegrafs/1234567878

[[outputs.influxdb_v2]]
urls = ["https://10.52.126.234"]

Environment info:

• System info: Run uname -srm and copy the output here
  Linux 4.15.0-124-generic x86_64
• InfluxDB version: Run influxd version and copy the output here
  InfluxDB v2.0.4 (git: 4e7a59b) build_date: 2021-03-15T07:37:28Z
• Other relevant environment details: Container runtime, disk info, etc
  Running as snap

Config:
Copy any non-default config values here or attach the full config as a gist or file.

[russorat]

connect #15721

[alv000h]

and this one #21009