Allow `JSON` for `TF_LOG_PROVIDER_{provider}` configuration

[timofurrer]

terraform-plugin-log version

v0.7.0

Relevant provider source code

n/a

Terraform Configuration Files

n/a

Expected Behavior

From the documentation I would expect that e.g. setting TF_LOG_PROVIDER_{provider}=JSON would result in logs in JSON with TRACE log level.

Actual Behavior

Using TF_LOG_PROVIDER_{provider}=JSON doesn't configure logging at all.

Setting TF_LOG=JSON works as expected though. And I cannot combine them since TF_LOG overrides the others.

Steps to Reproduce

Just set TF_LOG_PROVIDER_{provider}=JSON for any provider when running Terraform.
I'm using it when running provider acceptance tests.

References

[timofurrer]

I would also be open to contributing a fix if someone can point me into the right direction ...