Impl use of content of the service account key file in the environment variable YC_SERVICE_ACCOUNT_KEY_FILE

[GennadySpb]

Closes #39

[lbajolet-hashicorp]

Hi @GennadySpb,

I just left a quick suggestion to correct a typo, other than that, the code looks good to me.

If possible, could you rebase this on top of the current main and run make build-docs?
Since we moved from the old documentation system to the new, the documentation gets compiled in a different directory, and is being checked through an action, which is on main, but not on your branch since the PR was opened before this was made.
Otherwise since there's a couple of open PRs already is we can merge this one when you've fixed the typo, and we'll fix the docs before release, this implies main will be red for a while.

Thanks for taking care of this!

[lbajolet-hashicorp]

Small typo here

Suggested change

	Undefinded keyType = iota
	Undefined keyType = iota

[nywilken]

@lbajolet-hashicorp I went ahead and pushed up the suggested changes and generated the missing docs. I will merge once this goes green.