chore: Prepare release v1.2.0

[lantoli]

Description

Prepare release v1.2.0

Link to any related issue(s):

Type of change:

• Bug fix (non-breaking change which fixes an issue). Please, add the "bug" label to the PR.
• New feature (non-breaking change which adds functionality). Please, add the "enhancement" label to the PR. A migration guide must be created or updated if the new feature will go in a major version.
• Breaking change (fix or feature that would cause existing functionality to not work as expected). Please, add the "breaking change" label to the PR. A migration guide must be created or updated.
• This change requires a documentation update
• Documentation fix/enhancement

Required Checklist:

• I have signed the MongoDB CLA
• I have read the contributing guides
• I have checked that this change does not generate any credentials and that they are NOT accidentally logged anywhere.
• I have added tests that prove my fix is effective or that my feature works per HashiCorp requirements
• I have added any necessary documentation (if appropriate)
• I have run make fmt and formatted my code
• If changes include deprecations or removals I have added appropriate changelog entries.
• If changes include removal or addition of 3rd party GitHub actions, I updated our internal document. Reach out to the APIx Integration slack channel to get access to the internal document.

Further comments

[Copilot]

Pull Request Overview

This is a release preparation PR that adds the changelog entry for version 1.2.0. The PR documents new functionality for converting advanced cluster configurations to Provider 2.0.0 schema and improved documentation structure.

Key Changes:

• Adds changelog entry for v1.2.0 release with three enhancements
• Documents new advancedClusterToV2 command functionality
• Notes documentation improvements and variable support enhancements

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[marcosuma]

nit: there is a typo in the title of the PR

update: not anymore

[EspenAlbert]

🚀🚀🚀

[EspenAlbert]

[nit] Not sure about the usage of emojiis in the title. Looks a bit too much AI generated?

[lantoli]

that's fair, changed here: 6a70cbe