Added support for config_data

[eduanb]

Description

This PR allows you to send in the raw kubeconfig data without first creating a temp file.
Closes #1735

Note: I have very little Go experience, so please let me know if I need to change things. Would greatly appreciate it if someone could help with writing a test for this.

Acceptance tests

• Have you added an acceptance test for the functionality being added?
• Have you run the acceptance tests on this branch?

Output from acceptance testing:

$ make testacc TESTARGS='-run=TestAccXXX'

...

Release Note

Release note for CHANGELOG:

FEATURE:
Add `config_data` property to specify the raw contents of a kube config
...

References

Community Note

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• If you are interested in working on this issue or have submitted a pull request, please leave a comment

[hashicorp-cla]

All committers have signed the CLA.

[BBBmau]

Hello! I'll be taking a look at this PR in the coming weeks, could you provide a test for this new field in the provider? or a terraform config that will save the time to review this PR thoroughly. Thank you in advance 👍🏼

[BBBmau]

@eduanb pinging to be able to get a test config for this.