Trino user as a parameter for X-Trino-User

[amommendes]

Is your feature request related to a problem? Please describe.
Trino user can be used as an environment variable, but it can not be passed as a config.

Describe the solution you'd like
We could add a parameter to set on offline store configuration since X-Trino-User is required in the header.

Describe alternatives you've considered
If the idea is to set Trino user only as an environment variable, we could remove the user property from Trino client.