Add Random_String Implementation

[jamesptruitt]

476

PR Checklist

---

• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• My code follows the code style of this project.
• I ran lint checks locally prior to submission.
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Description

Add support for Terraform Random String resource so that the user can user the random strings for passwords and others purposes

Does this introduce a breaking change

• YES
• NO

Testing

Related PR in terraform-azurerm-caf
aztfmod/terraform-azurerm-caf#508

random_strings = {
jwt = {
length = 25
}
}

[arnaudlh]

thanks for the contribution @jamesptruitt