Feature Request

Proposal:

Add an option in inputs.exec and inputs.execd to pass custom environment variables to their child process.

Current behavior:

Currently, if you want to pass some values to the child process, you can only use the command line parameters or the whole environment of Telegraf.

Desired behavior:

For inputs.execd, there is always a single command so we could have an option like this:

[[inputs.execd]]

command = ["/path/to/my/process"]

[inputs.execd.env]
CUSTOM_VAR_1 = "var1"
CUSTOM_VAR_2 = "var2"
CUSTOM_VAR_2 = "var3"

Use case:

This can be useful to easily customize the child process behavior without having a separate configuration file and not display this information in the command line (e.g. for credentials)