feat: updates for HashiCorp Certified: Terraform Associate 004

[reubenjds]

Description

This PR updates the repository to align with the new Terraform Associate (004) exam objectives. It transitions the existing content from the 003 version to include newer features and organizational strategies now required for the certification.

Key Changes

1. Lifecycle Rules (4f)

• Added detailed notes on the lifecycle meta-argument.
• Included explanations for depends_on (explicit dependencies) and create_before_destroy (for zero-downtime updates).

2. Custom Conditions & Validation (4g)

• Added a section on validating configuration using precondition and postcondition blocks.
• Added a sample configuration demonstrating how to use these blocks within a resource to enforce infrastructure logic.

3. Ephemeral Values & Write-only Arguments (4h)

• Introduced documentation for handling sensitive and transient data.
• Explained the behavior of ephemeral values (not persisted in state) and write-only arguments (provider-side secrets).

4. HCP Terraform Organization (8c)

• Updated the Terraform Cloud section to reflect the branding change to HCP Terraform.
• Added information on how to organize infrastructure using the new Projects feature and how to manage Workspaces within those projects.

5. Documentation Mapping

• Updated the "Exam Objectives" markdown table to include the new 004 identifiers and links to the official HashiCorp documentation and tutorials.

[apraba05]

Great job Reuben!