fix(resource): fix schema and add tests for resource provider

[kuntzed]

Purpose

The schema for the resource provider resource and datasources is fixed and corresponding tests are added. Furthermore, some attribute names were improved.

Does this introduce a breaking change?

[ ] Yes
[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

[x] Bugfix
[ ] Feature
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

How to Test

• Test the code via automated test

go test ./...

• Additional test steps

...

What to Check

Verify that the following are valid:

• Automated tests are executed successfully

• ...

Other Information

Resolves #337

Checklist for reviewer

The following organizational tasks must be completed before merging this PR:

• The PR is assigned to the Terraform project and a status is set (typically "in review").
• The PR has the matching labels assigned to it.
• The PR has a milestone assigned to it.
• If the PR closes an issue, the issue is referenced.
• Possible follow-up items are created and linked.

[lechnerc77]

lgtm